Cat's Ear Hypochaeris radicata

I am an amateur naturalist trying to discover everything living in my garden.

 The pretty flower in photo 1 is Cat’s Ear - a common weed in my garden.  There are a number of superficially similar British yellow-flowered weeds  including  the Hawkbits, Sow thistles and the Hawksbeards I blogged here.  From my copy of The Wild Flower Key (Rose) I’m fairly confident my plant is none of these, though I’m less confident it is definitively Cat’s Ear (Hypochaeris radicata) and not the rather similar Smooth Cat’s Ear (H. glabra). The book tells me that were my plant to be Smooth Cat’s  Ear , then its yellow ‘petals’ would be only twice as long as wide (mine seem longer). Also that the green stems of H.radicata should broaden as they approach the flower head (more correctly ‘the involucre bract’), which appears to be the case for my plant (see photo 2). On this basis I’m going with the identification H.radicata.

Readers of my blog will know I try to do a little research to uncover some point of interest for each lifeform I come across. In the case of Cat's Ear my searches led me to an interesting paper [1] by N. Hartemink et.al. The authors asked the question "What does a plant do if you cut the flower buds off?" (these are my words - I'm paraphrasing). A trite answer would be "Grow some more!". Pausing to consider things in more detail however one might begin to imagine more subtle possibilities. Consider a plant growing in a field subject to heavy grazing by animals. If the plant loses a flower one might imagine various responses. For a short lived annual plant, flowering and successfully setting seed in a season is an absolute imperative. One might conjecture that such plants could respond to flower-loss by "stepping up" efforts to produce more and more flowers therefore in the 'hope' that some escape the grazing (of course plants don't 'hope' and this is a poor anthropomorphic description - but, hey, I'm an amateur and it's good enough for me!). By contrast, for long lived perennial plants, flowering does not  have the same urgency. If such a plant has its flowers removed, might it simply 'cut its losses' therefore, put 'on hold' attempts to flower and instead put its energies into growing more leaves and roots?

To add to these considerations, one should remember also that a plant may not have a simple unfettered 'choice' about whether and how many flowers to grow. Resources (food, water and light etc.) are always finite and may impose further constraints on what types of structure (e.g. flowers vs. leaves) the plant is able to produce. A deeper consideration of this resourcing issue has led the experts to formulate such theories as "meristem allocation". (Meristems are specialised regions of a plant where growth 'happens'. Meristem tissue is found at the tips of roots and shoots for example. It is made up of special meristemic cells that are rapidly growing, dividing and transforming into new bits of root, shoot etc.).  I don't understand the 'meristem allocation' theory in detail, but briefly it seems to revolve around the idea that a mersitem at the tip of a plant shoot has a 'choice' to simple carry on creating more and more plant shoot and leaves, or cease making leaves and shoots and instead switch to making a flower. Once the meristem has switched to making a flower however, there is no going back - that meristem is committed and can't later go back to making shoot. In a sense the plant's meristems are like cash in a bank. The plant can keep the 'cash' (mersitems) in the bank growing 'interest' (more shoots and leaves) or 'withdraw' (allocate) some money (meristem) and 'spend it' on a flower. This might all seem rather abstract, but the point is that armed with the idea that meristems are a fundamental unit of 'currency' in the 'economics' of plant survival, botanists can start to construct quantitative and predictive (as opposed to merely descriptive) theories of how plants ought to respond to different environmental pressures (grazing, resource shortages etc.).

So, what does a Cat's Ear do when you cut the flowers off?! Well, the authors above took three plant types: Cat's Ear, Devil's Bit Scabious (Succisa pratensis) and Brown Knapweed (Centaurea jacea). They found marked differences in the reponses of these three to removal of flower buds. Both S. pratensis and C. japea responded to flower bud removal by increasing the number of flower buds. Plants of both species would typically make around 7 flower buds per plant if 'left alone', whilst those plants who had their flower buds removed would 'bounce back' and regrow about 12. Interestingly however, S. pratensis also responded by switching some of its energies away from flower bud growth into increasing growth of plant side 'shoots' (strictly side 'rosettes' of new leaves). Appropriately for this blog posting, Cat's Ear's response was the most dramatic all. Plants 'left alone' produced around 60 buds. The 'decapitated' however, bounced back with a dramatic 240. There is much more in the paper that I could talk about, but I've gone on enough here and will simply refer you to the original if you're interested. What I like about the work is it is true science and yet an experiment that any motivated amateur could repeat and extend: find a patch of weeds and a pair of secateurs and you're all set to become a published scientist.

Reference:

[1]  Flexible life history responses to flower and rosette bud removal in three perennial herb, Nienke Hartemink, Eelke Jongejans, Hans De Kroon , Oikos 105: 159-167, 2004.

Scenedesmus algae

I am an amateur naturalist trying to discover everything living in my garden.

Some time ago I wrote about a puddle I spotted in my garden. Of course, I bought it into my house in a fishtank (doesn't everyone do this with their garden puddles?!).  It was only last week, nine months on, that I finally returned it to the great outdoors. Amazingly it was still brimming with microscopic 'pondlife', although it had become rather choked with the 'sludgy' cyanobacteria I wrote about here.

Over the months I repeatedly examined my puddle under the microscope. Photo 1 shows one of the lifeforms I found.  This one was rather common in the early days, but later seemed to disappear.

Spot something tiny and green under the microscope and its either algae or cyanobacteria. Cyanobacteria tend to be featureless, lacking detailed internal structure, notably a nucleus. The cells here have nuclei however, helping to identify them as algae. (The nuclei don't show up very clearly in photo 1 but by squinting I think you'll be able to see the spherical features towards the centres of the upper three cells).

Turning to my (borrowed) copy of the hefty "The Freshwater Algal Flora of the British Isles" (John, Whitton, Brook) - a 700-page light bedtime read! -  I was able to identify my algae as a member of the Scenedesmus genus. Characteristic features are the obviously 'pointy' crescent shape. Also, although I occasionally found single, isolated cells, very often I found 4 (as here) or 8 cells together (about which more shortly...).

Scenedesmus algae are part of the Chlorophyta (= the green algae). They are all freshwater. According to the book above as many as 200 different British species have been reported. However, it's been found that individuals from a species can grow into a variety of different forms as a result of different environmental stresses, so there's suspicion that many of these 200 'species' may not be unique. Furthermore the authors explain that recent scientific studies powered by advances in electron microscopy and modern-day biochemistry are pointing to a need to significantly rethink the traditional classification of many species. (This is happening everywhere in biology these days - see my posting on mushrooms here for example). All this means that although the authors give a key to the 42 British species of Scenedesmus algae they recognise, I've not attempted to pin down the species-identity of mine.

As I've said many times, I'm rarely disappointed when it comes discovering that there is some fascinating or unusual feature in the lifestyle of any creature I come across. Turning to my copy of R.E.Lee's Phycology (a present Christmas-last) it turns out that the fact I frequently saw 4 or 8 algal cells together was no accident.  If Scenedesmus is grown in a tank free from predators (such as grazing water fleas) it grows as single isolated 'unicells'. (If you're an algal cell wanting to maximise the amount of sunlight and nutrients reaching you its preferable to keep your distance from neighbours who might otherwise shield or shadow you). However, introduce some predators into the tank and, amazingly, Scenedesmus cells switch to growing in small groups as an anti-grazing defence! In the jargon, a group is known as a coenobium. Some groups also grow long spines, although interestingly the book implies that these are flotation devices to help the colony stay in the light, rather than anti-predator devices per se. The algae are able to detect the presence of predators by detecting chemicals ('infochemicals') in the water that leach from the digestive tract of the predators. Another of nature's tiny miracles!

A Mock Orange Tree - Philadelphus coronarius

I am an amateur naturalist trying to learn something about everything living in my garden.

Photos 1 and 2, taken a few days ago, shows the Mock Orange (Philadelphus) bush that grows at the back of my garden. It is a large plant (maybe 4m x 4m) and a fabulous site in early summer.

And yes, it smells as gorgeous as it looks! A rich honey/jasmine aroma that wafts across my lawn on summer evenings.

Philadelpus has long been popular with gardeners and plant nurseries stock numerous artificial cultivars. The Mock Orange (genus Philadelphus) and 'true' Orange (genus Citus) are really only distantly related. The genus Philadelphus is part of the large Hydrangeaceae family of plants.  I found a species-key here, and my plant keys out as Philadelphus coronarius.

Seeing a thin dusting of yellow pollen on many of the leaves I was inspired to get out my trusty student microscope. I enjoy fiddling around with microscopes and I'm a little surprised that in many years of doing so I've never before looked at pollen. For any beginnner like me who wants to have a go, there are a few tips it may help to know:

Firstly, something I hadn't previously realised is that plants release their pollen in a dehydrated state (15-35% water content is typical [ref.1]). I guess (but don't know) they do this to keep their weight low and so assist their transportation by wind or insects. Also, desiccation may help prolong the active lifespan of the grain. Dehydrated and hydrated grains can look significantly different (see photo 3).

A second thing it helps to know is that pollen grains often have a waxy surface coating. This can be a nuisance for microscopy as it may cause grains to stick together. It also obscures fine surface features of the grains.

Fortunately, both rehydration of pollen grains and removal of their waxy layer is easily achieved by simply wetting them with a few drops of alcohol.

Once you've looked at your pollen slide you can of course simply throw it away. Microscope users will know however, it is possible to make a collection of semi-permanent slides by encapsulating specimens in glycerine jelly. You can buy glycerine jelly especially designed for pollen. The jelly contains red dye that stains the grains and makes it easier to see fine details on their surfaces.

Anyway, photo 3 shows the results of the above: circular/triangular pollen grains about 12microns across.

Seeking to learn some more about pollen, I came across a nice review paper by Edlund et.al. here [ref.1]. The paper highlights various areas where the science behind pollen is unexplored or only partly understood. Take for example the functioning of the outer coating of pollen grains (the exine). This layer can be extremely ornate. Often it is riddled with cavities containing exotic plant proteins. When a dehydrated pollen grain lands on the 'female' stimga in the centre of a flower of the same species, something about the surface of the grain causes it stick fast, when pollen from a different species doesn't. The science behind this 'selective adhesion' is only partly understood.

Once a grain has stuck, chemicals are exuded by the stimga that rehydrate the pollen in a matter of minutes. Once again, this can be exquisitely selective. Two species of pollen grain can be put, side-by-side, onto a single stigma, and only the pollen grain from the correct species will be rehydrated. How nature manages to pull off this clever stunt is again something of a mystery.

With the grain re-hydrated, it germinates and sprouts a single tube that grows its way down the stimga. (There's a fun article by Chris Thomas here that describes how to observe pollen tubes by sprouting grains on a piece of onion skin).  Eventually the pollen tube contacts with a female egg at the base of the stigma and the pollen grain sends its DNA down the tube to fertilise the egg. (Pollen grains are a mechanism by which DNA is carried between plants. Its wrong to think of them as 'male sperm' however since a pollen grain is mostly comprised of bundles of 'normal' vegetative plant cells.)

Some plants rely on wind to spread their pollen. Others, animals and insects. Something new I learnt was that one plant- Lagerstroemia - is so keen to attract the latter it produces two types of pollen: a sterile, yellow, feeding pollen and a fertile, blue one.

My first microscope observations of pollen were great fun and I learned a lot. It turned out my Mock Orange had an another interesting microscopic feature for me. What it was however, will need to wait for another posting.


Reference
[1] Pollen and Stimga Structure and Function, A.F. Edlund, R. D. Swanson, Preuss, The Plant Cell 16:S84-S97 (2004)

Hedge Bindweed Calystegia sepium

I am an amateur naturalist trying to discover everything living in my garden.

Photos 1 and 2 show some Hedge Bindweed (Calystegia sepium) - a weed that pops up frequently in my garden.

My copy of The Englishman's Flora (Geoffrey Grigson) lists dozens of alternative names for this common plant, from the pretty Rutland Beauty, Shimmy-and-Buttons and Robin-run-the-Hedge,to the sinister  Devils Garter, Strangleweed and Devil's Guts.

A name not in the book is the one my mother taught  - Granny Pop the Bed - so called because if you squeeze the green base of the trumpet shaped head (see photo 2) the white flower pops out. It's not a very convincing pop it has to be said, but hey, when you're six its great!

In the jargon, the green flower base is called the calyx (I've labelled this in photo 2). The 'leaves' that make it up are called sepals. C.sepium also has an outer epicalyx.

When I first started this posting I took it for granted  that a web search would turn up scores of scientific papers on my common weed. As it turned out I struggled to find any! I did come across a research paper [1] on the apparently unusual lectin (a protein) biochemistry chemistry of my weed, but the subject matter was rather technical and I'm not expert enough to do it justice here. This aside most of the material I did manage to find concerned the related Field Bindweed (Convolvulus arvensis), a target for frequent study because it is a major weed of arable crops. (Field- and Hedge Bindweed can be readily distinguished by  knowing that Field Bindweed doesn't have an epicalyx).

This lack of literature meant that for a time I was left wondering what to say in this post, but then I recalled an unusual fact concerning Bindweed's spiral growth which I'd read about some time ago (I don't remember where). Photo 1 shows a plant climbing a garden cane. As it climbs the stalk is seen to spiral in an anticlockwise direction (as viewed from above). What's interesting is that C.sepium always spirals anticlockwise. (I've even been around my garden checked! Indeed once you know this fact, its hard resist the temptation to check the spiral of every Hedge Bindweed you see anywhere!).

This feature of always twisting one way  turned out to be rather a rich topic for exploration. Amongst others I was led to a paper by Thitamdee et.al. [2] on the origins of spiral forms in plants:

The authors' studies focused on plant microtubules.  These are molecular sized rods found in both plant and animal cells (they've received mention on my blog before, here). Its been discovered that large numbers of these rods decorate the surface of plant cells (like matchsticks stuck on a balloon). The rods do not lie randomly on the surface of the cells however, rather they order themselves so as to line up along a common direction. There's some amazing video of real microtubules jostling about on cell surfaces on the webpage of Indiana University's Shaw Lab. here.  Now, to continue the balloon analogy, imagine having a lot of matchsticks densely glued to the surface of one of those sausage shaped party balloons. Imagine the matches are all lined up so as point around the short, circular axis of the balloon (like hoops around a barrel). Next, imagine blowing more air into the balloon. Though I haven't actually done the experiment, I hope its reasonable to suggest that the rigid matches would make it more difficult for the balloon to swell  in circular cross-section (get 'fatter'), and instead the balloon would grow more freely lengthwise (get longer). This is exactly what aligned microtubules are believed to do for plant cells  i.e. cells that would otherwise grow and expand as simple spheres are instead constrained to grow and expand along a preferred direction. This is useful because it allows the plant to create e.g. long, thin cells suitable the plant stalk. (Actually, strictly its not microtubles themselves that constrain the growth of the cell walls,  rather the microtubles appear to act as markers for the laying down of a secondary stiffening material - cellulose - but the principle's the same)

Now, Thitamdee et.al. were studying a cress plant called Arabidopsiss. This is famous amongst botanists as the plant for genetic studies worldwide. Normal Arabidposis plants don't spiral,  they grow straight. Furthermore, when scientists looked at the microtubules on cells in the stalk they found them to be arranged exactly as in the description above (i.e. 'hoops around a barrel')

What Thitamdee et.al. discovered however, was that a mutation in a single gene can cause a change in the way microtubles on cells in the stalk of an Arabidopsis plant arrange themselves. Specifically, they observed mutations that caused the microtubules to shift from being aligned all-parallel to the cell circumference ('hoops around a barrel') to instead all lying on the cell surface at an angle to the long axis of the cell.

And what did these mutant plants, with their slanted microtubles, do? Yep, grow in a spiral!

The importance of this work is that it implies an explanation for why some plants spiral and some don't, and furthermore why, for many species, every individual must spiral in the same direction: Things are dictated by the angle at which microtubles are aligned on the cells. This in turn is hardwired by the plant's DNA.  Perhaps an ancient ancestor of Hedge Bindweed grew straight. At some point however a gene mutation arose that caused the microtubles to align at some new angle. With this angle fixed by the DNA, the Bindweed's fate was fixed; Subservient to the constraining forces acting on its cell walls, it was doomed to spiral, and always in the same direction, this being dictated by the angle of microtubule alignment (though what this is specifically I don't know -  I haven't found any reference to suggest the microtuble alignment of C. sepium specifically has been studied).

To end, a bit of humble pie. When I first recognised the anticlockwise spiralling of Bindweed, I admit I thought I was rather clever in having uncovered some little known fact... until, that was, I discovered that my supposed 'little known fact' even had its own popular 1950's song!

The fragrant honeysuckle spirals clockwise to the sun, 
And many other creepers do the same.
But some climb anti-clockwise, the bindweed does, for one,
Or Convolvulus, to give her proper name... 

( from Misalliance by Flanders and Swann, ).

References

[1] 

The Crystal Structure of the Calystegia sepium Agglutinin Reveals a 

Novel Quaternary Arrangement of Lectin Subunits with a Prism Fold,  Y Bourne et.al., The Journal Of Biological Chemistry, 279(1),pp. 527–533, 2004

[2] Microtubule basis for left-handed helical growth in Arabidopsis, S. Thitamadee, K. Tuchihara & T. Hashimoto, Nature, 417, p.193, 2002.

Greater Plantain Plantago major

I am an amateur naturalist trying to learn something about everything living in my garden.

Taken in August, photo 1 shows a specimen of the weed Greater Plantain (Plantago major) growing on my lawn. This plant is very common in the UK and likely to be encountered on any patch of rough wasteland (= my lawn!).

For such a common plant I have found relatively few freely available papers dealing with Greater Plantain on the web. There are a number (such as here and here) that deal with its medicinal properties. Plantago major appears to have a long list of antibacterial, antifungal and antitumeral properties and has even been recommended to treat the bites of rapid dogs! Amongst the interesting snippets I picked up from skimming the paper by Velaso-Lezama et.al. [1] is that Greater Plantain is today used as a medicinal tonic in Mexico having been originally introduced there by the Spanish conquistadors.

A number of species of Plantain grow in the UK including Ribwort- and Buck's Horn- , both of which have narrower ('lanceolate') leaves than Greater Plantain. Also Hoary Plantain (Plantago media) which as the name implies differs from Greater Plantain in having greyish down on the leaves. That at least is how things are set out in my copy of The Wild Flower Key (F. Rose, publ. Warne). If however, the Plantago media above is one and the same as the Plantago intermedia described in this paper [2] by El-Bakatoucshi et.al., then these authors cast doubt on whether major and intermedia are sufficiently distinct to be regarded as separate (sub) species.

In skimming the paper above by El-Bakatoucshi et.al. , a word I came across that was new for me was protogynous (in context: "Plantago major is protogynous"). A little research and I now understand what this means. I'll share it here for interested readers: Firstly one has to recall that for many plants, the flower is typically neither male nor female. Rather the same flower combines male pollen producing parts (the anthers) and a female reproductive part (the stigma). This gives plants an issue of how to avoid self-fertilisation (i.e. self pollination). Plants have come up with a variety of solutions including i) Ignore the problem (= allow self pollination) ii) Separate your line into two, so that some plants carry only male and others only female parts (these are the so-called dioescious plants - from the Greek "two houses" . Our old friend the stinging nettle is an example) iii) Develop some "chemical / structural" approach that avoids self pollination. I wrote about a classic example when I discussed the two types of primrose, 'pin' and 'thrum' iv) Separate the time at which the male and female parts of a flower are active / receptive. This latter method ('iv') is protogyny and is the technique adopted by Greater Plantain. The female stigmas of Greater Plantain flower are protruded 1-3 days before pollen is produced and in this way the chances of self pollination are reduced. Another of those small but elegant behaviours Mother Nature has carrying on all around us.

References
[1] Effect of Plantago major on cell proliferation in vitro R. Velasco-Lezama et.al., Journal of Ethnopharmacology 103 (2006) 36–42

[2] Introgression between Plantago major L. subspecies major and
subspecies intermedia (Gilib.) Lange. in a British population, R. El-Bakatoushi et.al. , Watsonia 26: 373-379 (2007)

Smooth Hawks-beard Crepis capillaris

I am an amateur naturalist trying to learn something about everything living in my garden.

I have mentioned previously that the pleasure for me in maintaining this blog is that some previously unnoticed (by me at least) plant or insect, once researched, takes on a whole new aspect. So it is with today's posting. A scattering of facts about the genetics of an inauspicious weed may seem obscure to some, but for me, a weed on my lawn catches my eye with a new interest these days. Photos 1,2 and 3 shows said weed. It pops up frequently in my garden.

For the unskilled amateur botanist (=me!) identifying yellow flowered weeds isn't altogether trivial as the guide books contain a long lists of yellow-flowered ragworts, fleabanes, marigolds, colts-foots, dandelions, sowthistles, cats'-ears and hawkbits. After a little work however I'm fairly confident my plant is none of these and is instead Smooth Hawks-beard (Crepis capillaris). A characteristic feature of the Hawks-beards are 'involucre bracts' (=the little leaves around the base of the flower head - best seem in photo 2) organised in distinct inner and outer rows.

Surprisingly, although it is a common UK weed, I've been able to find almost no detailed online information on Smooth Hawksbeard. One exception is the bioimages site that lists a handful of fungal rusts (including some Puccinia species - see my post here) and a gall fly known to parasitise Hawksbeard. The other exception was an online paper by Oud et.al. [1] that describes the chromosomes of C. capillaris. With my comments of the opening paragraph above in mind, its this I'll discuss.

As most people know, the DNA inside cells is packaged into structure called chromosomes. When new cells are needed by a body, the existing cells set about creating copies of themselves by dividing into two, in a process known as meitosis. (Cells destined to become specialist structures such as sperm or eggs do something slightly different called meiosis, but never mind that here). To create two cells from one its clearly necessary to replicate the DNA. To do this the chromosomes perform a complex little 'dance' inside the cell in which they double in number (in a process called interphase), pair up and line up along of the middle of the cell ('prophase' and 'metaphase' respectively) and finally split apart ('anaphase') as the cell separates into two ('telophase').

I got the hang of this terminology recently using my colouring crayons! (I've a copy of the very clever - 'The Botany Colouring Book', Young - in which you learn by doing). You can find any number of explanations on the web however (here for example).

It's perfectly possible to watch the whole miraculous 'chromosomal dance' down a hobbyists microscope. The classic place to look is at the growing tip of a young plant root where new cells are being feverishly created to grow the root. Indeed, I've tried looking for it myself a few times. I've yet to succeed in getting any really good results, but rest assured when I do there'll be a posting...

I can't resist a small digression at this point to mention microtubules. When it comes to pulling chromosomes apart (i.e. during anaphase), cells do this by strapping tiny cables (microtubules) to chromosomes in a process akin to hauling logs out a log pile by pulling on ropes. These microtubules are tiny (around 25nm across where a 'nm' is a millionanth of a millimetre) and hollow. So tiny are they that some physicists (notably the famous blackhole physicist Roger Penrose) have even speculated that inside microtubules, reality ought to be dominated by the small and weird world of quantum physics (cats being both alive-and-dead; particles being in two places at once - that sort of thing) and that signals propagating inside microtubules in the brain might have something to do with the mystery of human consciousness (you can listen to Penrose give a lecture on it here). Anyway, this is a highly contentious claim and a long way from today's discussion. To return to more certain issues:

In their paper above Oud et.al. set out to study the three-dimensional arrangement of chromosomes inside replicating cells during prophase. It turns out if you want to study chromosome arrangements inside a cell without being mired in complexity, you can do worse than make use of Smooth Hawks-beard since it has a mere 6 chromosomes (strictly one should write '2n=6' - see my previous explanation here). Compare that with humans with (2n=) 46, or some ferns with around a thousand! (I have no idea why there is such variation in nature. Generally, there is no relationship between the number of chromosomes and the complexity of an organism. Anyone?).

Trying to image the three-dimensional arrangement of tiny objects is not simple when you remember that looking down a conventional microscope all you see is a flat, two-dimensional view of an object. To achieve a 3D visualisation of chromosomes Oud et.al. used a special type of microscope known as a confocal scanning laser microscope. As anyone who has a normal microscope knows, images suffer from a limited 'depth of field': only a portion of your object appears in focus. Other parts of an object, at different depths, appear blurred. Often this is a nuisance, but confocal microscopes cleverly use it to advantage. They physically block out light from anywhere other than the one extremely thin section of a sample that happens to be in focus. The advantage of this may not be immediately clear, but the point is that by slowly varying the point of focus, one can build up a stack of images where each image contains only light coming from that single, selected slice through the sample. By taking a bunch of such images from different depths, and stacking them all together (using a computer) one arrives at a three dimensional image.

Using this method Oud et.al. arrived at the wonderful picture of the three dimensional arrangement of chromosomes in a Smooth Hawks-beard root cell in their paper. Of course, their study was not about making 'pretty pictures'. They were interested in adding to biologists' long-standing interest in knowing how chromosomes are arranged in space inside the nuclei of cells; In particular whether the arrangement is random or not. Their conclusion (as I understand it) was that although a range of differing arrangements were observed across cells, overall the chromosomes seemed to arrange themselves in space in a finite number of non-random ways.

So there we have it! A week ago, for me, an unknown weed. Now, a named plant with a intriguing inner life. Bye for now.

Footnote:
I have begun to think that my habit of normally giving only a link to articles isn't the best, as articles may disappear online in future. From now on therefore, I'm going to make an effort to selectively include proper references at the end of postings. To that end:
[1] Oud JL, Mans A, Brakenhoff GJ, van Der Voort HT, van Spronsen EA, Nanninga N. Three-dimensional chromosome arrangement of Crepis capillaris in mitotic prophase and anaphase as studied by confocal scanning laser microscopy. J Cell Sci. 1989 Mar;92:329–339

Lady's Smock Cardamine pratensis

I am an amateur naturalist trying to learn something about everything living in my garden.

Photo 1 shows an attractive flower I found growing wild in a neglected corner of my garden early last summer.

A little time spent with my trusty copy of The Wildflower Key (Francis Rose) and I'm fairly confident my plant is Lady's Smock. The leaves of my plant are also rather characteristic (photo 2) with the lower leaves tending towards round with the largest leaf being the one furthest from the stem, whilst the upper leaves are rather long and narrow.

My copy of The Englishman's Flora (Geoffrey Grigson) lists around thirty alternative common names for Lady's Smock from the pretty Cuckoo Bread, Cuckoo flower, Lucy Locket and Milking Maids to the less flattering Pig's Eyes and Bog Spink!

The scientific name for my flower is Cardamine pratensis. Pratensis is from the Latin 'of meadows'. From some web searching I understand Cardamine owes its heritage to the anicent Greek physician Dioscorides (ca. 50AD) who used the name for some cress-like plants, karda being Greek for 'heart', and damao to 'tame or overpower'. (I've read that Lady's Smock is an edible, spicy, salad leaf, though I can't vouch for the truth of this.)

Lady's Smock is a favoured food of the caterpillars of the Orange Tip butterfly.

C. pratensis is a perennial, native to the British Isles and is highly variable. The paper here gives a flavour of the lengths the professionals have gone to in attempting to characterise it. My copy of New Flora of the British Isles (Stace) sums things up rather bluntly however as "impossible to subdivide usefully; identity of [named] variants [...] is very dubious". My attempt to get some basic amateur understanding of the issue led me into a study of polyploidy. I'm certainly no expert on genetics but briefly my understanding is this:

As most people know, at times the DNA inside living cells gets packaged into structural units, the chromosomes. A microscope reveals we have 46 chromosomes. Closer investigation reveals that these 46 are in fact present as two largely similar sets of 23 i.e. 23 chromosomes from our mother and a similar 23 from our father. (The phrase 'largely similar' skips over a wealth of detail, such as the fact that a certain chromosome from our mother might carry a different characteristic, say eye colour, to that from our father etc. - but never mind that here) . For humans we say "2n=46". Other mammals have other chromosome counts, for example I read variously on the web that the kangaroo has a mere 2n=12 whilst the European hedgehog boasts 2n=88 (in general there is no link between chromosome number and the size or complexity of a creature).

In the case of many plants, a lesser number of insects, amphibians, fish and a very few mammals (one being an Argentinian Plains Rat - see the parade of polyploids here!) however, things are more complicated. Some varieties of strawberry for example contain not, as we humans, two largely similar sets of 23 chromosomes but no fewer than eight sets of seven chromosomes. This gets written as "8x=56". This condition of having more than two sets of chromosomes is termed polyploidy.

The fact that more than 30% of plants go in for polyploidy would seem to indicate it must have some important benefits. There are many theories as to what these benfits might be. It's been suggested for example, that polyploidy may promote greater variation in a species and thereby help it evolve ('radiate') more easily into new environments, or that polyploidy may provide protection against 'in-breeding' issues that might otherwise arise for plants that self-fertilise. It seems also that some polyploids are healthier and more vigorous than non-polyploids. In all however, there seems to be no universally accepted theory of why so many plants are polyploids. Another of nature's mysteries!

Anyway, all of this preamble basically allows me to comment that my garden weed occurs in a bewildering variety of genetic 'forms' from the 'diploid' 2n(=2x)=16 through types with chromosomes numbers of 14, 15, 16, 19, 20, 21 – 28, 30, 32, 37, 42, 44, 45 and 48.

After the science, who better to have the last word than the Bard. From the song 'Spring' at the end of Love's Labour's Lost:

When daisies pied and violets blue,
And lady-smocks all silver white,
And cuckoo-buds of yellow hue
Do paint the meadows with delight,

Couch Grass (Elymus elegans) and Perennial Ryegrass (Lobium perenne)

I am an amateur naturalist trying to learn something about everything living in my garden.

Success in discovering the identity of some plant or animal is all about the careful and methodical observation of details. I've written this before, and had I only paid attention to my own dictum, I might avoided wasting half a morning recently getting thoroughly confused over the species of some grass growing in a corner of my garden!

Intrigued by a comment in a booklet Practical Microscopy (Eric Marson, Northern Biological Supplies) - a superb guide I cannot recommend too highly to any amateur interested in preparing their own high quality microscope slides - I had set out to examine some blades of grass under my microscope.

Venturing into my garden I came across the grass in photo 1. The long, seed bearing structure is technically termed a 'spike'. I picked a little and came back inside but before putting it under the microscope I decided to try identifying the species using my copy of Grasses (Fitter et.al. publ. Collins). Having only a few inches of specimen, it wasn't long before I was stuck however. I went back outside therefore, found my clump of grass and picked a little more. Embassingly foolish as it seems now, this went on for nearly an hour, with me traipsing back and forth, collecting a little more grass each time and returning inside only to find myself more confused than ever.

Finally, in exas- peration, I threw away my growing collection of tattered grass cuttings and started a fresh, and this time, methodical study. The result was the arrangement in photo 2 and the belated realisation I'd been collecting bits of two different grasses!

The two in question are Couch grass (Elymus repens) (photo 2, upper) and Perennial Ryegress (Lolium perenne). Laid out neatly in photo 2 the differences are obvious. I can say that it underlines the lesson that one cannot trust that causal glance at that seemingly undifferentiated clump of 'spike bearing' grass swaying in the breeze!

One difference between the two grasses in photo 2 is leaf size. In fact however, this is not an overly useful guide to species identification, as the size of the leaf baldes can vary with their position on the 'stalk' (culm) and other factors (soil quality etc.). Instead, amongst the most useful guides to a grass's species is the shape and size of the ligule, a small vestigial leaf-like structure the nestles between the culm and a leaf. Photo 3 shows the ligule of Perennial Ryegrass. By contrast, Couch grass lacks a ligule (though just to confuse the unwary, the leaves wrap around the culm via two little sheath-like flaps know as auricles - see photo 4).

Returning to the spikes of my two grasses, photo 5 shows a closeup of both. These bear the grasses' minute flowers (the source of all that hayfever-inducing pollen in summer). As I learnt in my previous study of the Cultivated Oat (Avena sativa), the structure of grass flowers comes with a lot of botanical jargon. I'll not repeat it here, but for completeness I've labelled up photo's 6 and 7.

And what of that micro scope image I originally set out to acquire? Well, as everyone knows you can get a painful cut from the edge of a blade of grass. Putting one under the micro scope (photo 8) shows just why: a margin decorated with a row of tiny saw-toothed daggers. Another of nature's tiny miracles.

A Snowdrop Galanthus

I am an amateur naturalist trying to learn a little about everything living in my garden.

Hot on the heels of one of my favourite garden birds, one of my favourite flowers: The Snowdrop (the photo was taken back in mid-February)

Snowdrops are members of the plant genus Galanthus (from the Greek 'gala'=milk, 'anthus' = flower). What I've learnt about them has been mostly through Mark Smyth's very nice Snowdropinfo website, the Royal Horticultural site, the BBC site, and from my trusty copy of The Englishman's Flora (Geoffrey Grigson).

Firstly, regarding the name, both the RHS site and Grigson state that 'Snowdrop' derives from the German word Schneetropfen, a type of ear ring popular in the 16th and 17th century. Now, whilst I'm entirely happy to accept this, neither author gives a reference without which it's not immediately obvious to me that likening this plant to a 16th century German earring is more likely than people having chosen the 'Snowdrop' after... er, well...drops of snow! (Anyone?)

Geoffrey Grigson lists other folk names including Eve's Tears and Candelmas Bells, the latter a reference to the Christian festival of February 2nd when Snowdrops are one of the few plants in flower.

The snowdrop, in purest white arraie,

First rears her hedde on Candlemas daie

(Early church calendar of English flowers, c. 1500 - see here)

According to the BBC's site, bringing Snowdrops into the house at Candelmas symbolises a death.

Snowdrops are widely spread across Europe and Asia. There are nineteen true species (there's a list on Wikipedia's Snowdrop page) and literally hundreds of artificial cultivars, with new ones created all the time by enthusiasts ("Galanthophiles"), and old varieties occasionally re-discovered in sleepy vicarage gardens or (see the National Trust site here) on overgrown Victorian rubbish dumps!

You can find a photo-gallery of cultivars on Mark Smyth's site. What characteristics elevate nineteen types of Snowdrop to true species level I'm not sure (anyone?). My copy of 'The Wildflower Key' (Francis Rose) lists only one for the UK - Galanthus nivalis.

The chemical Galantamine was first isolated from Snowdrops and today finds medical application in the treatment of Alzeimer's disease.

Finally a few words on Snowdrop pests and diseases, of which there are various: The RHS site describes the two fungi Botrytis galanthinae and Stagonospora curtisii as 'the bane of many snowdrop growers.' Snowdrops are also attacked by the larvae of the Swift Moth and the stem nematode worm (Ditylenchus dipsaci) (you can download a pdf file about the latter here). Prize for impressive pest has to go to the Narcissus fly (Merodon equestris) however. This black-and-yellow insect wards off predators by mimicking a Bumblebee. You can find some photo's at the insect images website. Painful as it will be to the ears of gardeners, and although I enjoy my garden's snowdrops far too much to want to see them all wiped out, as an amateur naturalist I have to say I wouldn't mind sacrificing just one or two bulbs for the chance to see one of these flies for myself!

Haematoccus algae

I am an amateur naturalist trying to learn a little about everything living in my garden.

Recently, in the interests of finding some life-form with which to entertain the legions of avid readers of this blog (hem, hem), I decided to investigate what life might exist in a small pool of rainwater that had collected in the crevices of a sheet of polythene lying in my garden. Putting a drop under my hobbyist's microscope I was immediately confronted by large numbers of the creature seen in photo 1 (scale:1 small division = 1um). Some were motionless. More excitingly, others were highly active, 'zooming' through the water at a rate of knots (see later)

Some internet searching later, and with the help of photo's such as those on Ralf Wagner's microscopy site, and I'm tolerably confident I'm looking at a Heamatoccus alga.

The red colouration, motile behaviour and the presence of the transparent, gelatinous envelope surrounding the central green body all fit with the the species being H. pluvialis on this site ('Algaebase') . I don't claim any certainty over this identification however, since firstly I'm no expert, and secondly the same site lists 5 other species in the Haematoccus genus and a staggering 123,336 species of algae overall.

The family Haematoccae is part of the Volvocales order of algae, one example of which - Volvox - is a perennial favourite with microscopists. The Volvocales are equipped with two whip-like flagella - the secret to their ability to 'swim' through the water. The length and positioning of any flagella on an alga is an important aid to identification. Unfortunately the quality of my camera/microscope optics doesn't appear to be good enough to have caught these in the (dormant) Haematoccus specimen in photo 1 (or is it that flagella are lost in the dormant state?) - but the superb photo's by Wim van Egmond here show them clearly.

In researching the life in my garden I constantly come across what I imagine at first to be 'obscure' creatures. "Beyond naming it, surely no-one can have found the time to learn anything interesting or remarkable about this little critter!" I think to myself. It's a constant source of enjoyment to me to learn I'm wrong, and that for just about anything I come across, someone somewhere will have discovered some remarkable or interesting 'story' (which isn't to say that vast amounts don't remain unknown about the natural world of course).

So it was with H. pluvialis. Beyond a few dry descriptions in an obscure journal, surely there would be nothing say? Wrong again! It turns out H.pluvialis is an algae of significant commercial importance. It produces the highest known concentrations of astaxanthin of any living creature and is cultured on a commercial scale. Astaxanthins are chemicals used in the cosmetics, food and feed industries. They are antioxidants and have been studied for their potentially beneficial effects against everything from cataracts to colonic cancer. Guerin et.al. have produced a review (Trends in Biotechnology, 21(5), 2003). Astaxanthins are cartotinoid chemicals responsible for the red coloration in photo 1. They act as a 'sun block' against harmful UV rays. Those dormant algae I observed in my microscope sample seemed to contain more red pigment than mobile ones. I assume this is because dormancy is, in part, a mechanism to survive in dry conditions when cells can expect to need more protection from the sun.

Algae introducing astaxathanins into the food chain is the reason why animals higher up like shrimps, salmon and flamingos end up with pink flesh or feathers.

Returning to the issue of the mobility of H.pluvialis, Burchardt et.al (Biodiv. Res. Conserv. 1-2, 163-166, 2006) give a figure for their swimming speed of 200m/h. Given that their size is about 20um, scaling this up, and assuming a human about ~2m tall and I've got my maths right, this corresponds to a person swimming along at 20,000 km/h!

Finally, I can't end without mentioning one of the few books I have that gives a fairly detailed introductory guide to freshwater algae, namely Freshwater Microscopy by W.J. Garnett. Though it contains no real information about Haematoccus beyond a mention, it covers many common UK species in some detail. First published in 1953, I particularly like dipping into it for its evocation of a seemingly quieter more 'holistic' (for want of a better word) world, before out-of-town shopping centres and a life of frenzied commuting up-and-down packed motorways, when armies of amateur hobbyists seemed to spend their evenings and weekends learning the art of painting watercolour landscapes, investigating the geology of their county, or studying the lifeforms in their village pond. Or perhaps that's rose-tinted nonsense, though I do wonder how many hobbyists there are today, who, of a typical weekend, boil hay in rainwater in order to culture pond protozoa for study as Mr Garnet advises!

On the other hand I may be entirely wrong and there are legions of you hay-boilers out there! If you're one such, do leave a message to say hello.

daffodil narcissus

I am an amateur naturalist trying to learn something about everything living in my garden.
Spring has sprung here in Oxford in the U.K. One of the cheeriest signs of its arrival is surely the great profusion (I'll spare you references to "hosts of golden-" etc.!) daffodils that pop up in our gardens, woodlands and on roadside verges. Photo 1 shows some of those appearing anually in my garden.

In fact, a number of different types of daffodil appear at this time of year in my garden. That I should find more than one is perhaps no surprise since, as I learn from the Warwick Daffodil Genetic Resource webpage, breeders have developed a staggering 25,000 daffodil cultivars! The Royal Horticultural Society site hosts a searchable database. The same site also gives details of the horticultural code system used by daffodil aficionados (narcissists?!) to label varieties. In brief, it works like this:

Firstly, decide which of the 13 divisions of daffodil yours belongs to. In the case of the daff in photo 2, though not obvious from the photo, I measured the central 'trumpet' (corona') as longer than the outer petals ('perianth segments'). This puts it in Divison 1. By contrast, the corona of the daffodil in photo 3 is more than 1/3, but less than the full length of the petals, putting it in Divison 2.

Next, write down a letter for the colour - White, Green, Yellow, Pink, Red or Orange - of the perianth segments. So, photo 2 becomes 1Y, and photo 3 2W. (There are rules on the RHS page above for what to do if your daffodils petals are multicoloured)

Finally, repeat for the corona (adding a hyphen '-'). So finally photo 2 = 1Y-Y and photo 3=2W-Y.

Simple! (Or at least that's my understanding - as always, my amateur identifications come with a health warning - I'm always happy to be corrected. )

Of course it's also possible to be more 'botanical' about things - working through phrases like 'dentate coronal rim'. The ultimate goal must surely be to pin down one's daff's to one of the >25000 listed varities. Breeders have come up with some great names - "Her Majesty Queen Alexandera"; "This Little Piggy" and "Singing Pub" being three that caught my eye. I'd be delighted if any expert out there can tell me the name of the daffodil's in Photos 2 and 3 .

For those interested in doing more than simply naming their daff., the definitive textbook would appear to be "Narcissus and Daffodil, The Genus Narcissus" (Edited by Gordon R. Hanks, publ. CRC Press). I don't own a copy, but rather helpfully, the publishers have put a substantial chunk of the book online. From this I learn that there are about 80 species (as opposed to sub-species cultivars) of Narcissus, forming part of the Amarillidacyeae family of plants that also includes the snowdrops and lillies. Something I'd not really considered was how bulbs grow and expand. The book gives a rather detailed account of this and explains that each year new flesh appears in the centre of the bulb, with progressively older flesh being found further out from the centre. The very oldest flesh ends up as the papery, thin skin one often finds on the outer surface of bulbs. Finally, it seems that daffodil bulbs contain some rather nasty, toxic, alkaloid compounds. This no doubt explains why, although bulbs in my garden commonly get dug up and eaten (by, I assume, squirrels or badgers), this never seems to happen to my daffodils. Britain's wild daffodil is Narcissus pseudonarcissus.

The 1st March is St. David's Day - the patron saint of Wales - and it's common for people to wear a daffodil buttonhole.

I'll leave two last words to William Shakespeare:

When daffodils begin to peer,
with heigh' the doxy, over the dale,
why, then comes in the sweet o' the year.
The Winter's Tale (Act 4, Scene 3)

and from the same play

Daffodils
That come before the swallow dares,
and take The winds of March with beauty
The Winter's Tale (Act 4, Scene 4)

Sun Spurge Euphorbia heliscopia

I am an amateur naturalist trying to discover everything living in my garden.

After a series of postings on some of the smaller and arguably more curious lifeforms present in my garden, today's posting features something I suspect most of you will find all too familiar: a garden weed.

Growing in my vegetable patch (at (0.1,1.7) - see here) is the weed seen in photo 1 (click photos to enlarge). It has quite happily survived the British winter frosts.

Working with my copy of The Wild Flower Key (F. Rose, Penguin), I had no difficulty in identifying my plant as a member of the (amusingly named) spurge family (supposedly a word derived from 'to purge' - a reference to the plant's laxitive effect). There are over a dozen British spurges however, so identifying the species involved slightly more work, but on the basis that my plant has a smooth (non-hairy) stem; leaves edged with tiny teeth, arranged in alternating fashion along the stem; and a "flower head" (umbel) with five-fold symmetry - together with a few other features relevent to the key in the book above - I'm identifying it as Sun Spurge (Euphorbia heliscopia).

Sun Spurge is normally a single-stemmed plant. Occasionally however, as in photo 2, it may banch from the base (since this plant is a common weed in my garden I felt no compunction in pulling it out to photograph it).

Photo 3 shows Sun Spurge's five-fold symmetric 'umbel'. The five leaves at the base of the umbel are known as bracts. The individual 'cups' containing the tiny central flowers are known as involucres.

An obvious feature of Sun Spurge is that the flower-head is almost entirely green. Since much of any plant's effort goes towards harvesting sunlight, it clearly makes sense to pack every available surface with green chlorphyll. What puzzles me is that most plants don't do this however. Instead they use up precious resources producing brightly-coloured flowers, the said purpose being to advertise their presence to pollinating insects (or so I understand). The question I then have however, is why Sun Spurge doesn't need to do the same? Can anyone comment?

Reminding me of piece of surrealist sculpture from an Yves Tanguy painting, Photo 4 shows a closeup (40x magnification) of one of the tiny flowers of Sun Spurge, peppered with yellow pollen grains. My understanding is that the small, green, plate-like 'petals' nearest to you are nectar producing glands. The round object in the background is the plant's ovary-containing female fruit. The three forked prongs sticking up from it are stigmas. A pollen grain landing on one of these will fertilise the ovary, causing the fruit to swell up, eventually to the point of bursting when it explosively scatters seed over the surrounding soil.

Sun spurge is part of the large Euphorbiaceae family of plants comprising some 7,50o species. The leaves are a favoured food of the caterpillars of the Spurge Hawk moth (a migrant visitor to Southern Britain). When broken, the stem bleeds a milky-white sap and from my copy of Medicinal Plants In Folk Tradition (Allen and Hatfield, Timber Press) I learn that our ancestors used the sap to cure warts. I certainly don't advise anyone try this however since the sap is a serious irritant and worse, a carcinogen. If that isn't enough to deter casual experimentation, as the book describes, one man given a dose 'as a joke' (!) in the ninteenth century:

'ran up and down the street like a madman, and swelled so big that his friends had to bind him round with hay-ropes lest he shall burst'

With friends like that who needs enemies!

Yellow Corydalis Pseudofumaria (corydalis) lutea

I am an amateur naturalist trying to discover everything living in my garden.

Growing wild under the hedge at rear of my garden (at (0.8,2.0) - see here) are a number of patches of the yellow-flowered plant seen in photo 1 (taken back in early summer) . Photo 2 (click on photo's to enlarge) shows a close up of the pretty, trumpet-shaped flowers.

A short time spent with my copy of the excellent Wildflower Key (Francis Rose, Warne 2006) and I'm confident in identifying my plant as Yellow Corydalis (Psudeofumaria (Corydalis) lutea).

From the book above I learn that the plant family the Fumariaceae (the Fumitories) are related to the poppies (see here). The book lists eleven British species. From Wikipedia's entry however, it seems there is some debate amongst botanists as to whether the the Fumariaceae truely constitute a plant family.

The book describes Yellow Corydalis as introduced to Britain from E.Europe, though "possibly native in Kent". I can say that having learnt to recognise it, I've found it to be quite common, growing wild in Oxfordshire.

Confusingly, the official Latin name for Yellow Corydalis has changed from Corydalis to Pseudofumaria, to reflect that fact that the members of the former plant genus have simple stems whilst the latter have branched stems.

Turning to the internet I can find almost no information specific to my Yellow Fumitory (if anyone can point me to some do please leave a comment). I have come across a range of descriptions of its cousin pink-flowered cousin, Common Fumitory (Fumaria officinalis) however. Common Fumitory is distinguished by having a single seeded fruit (achene) whilst the other fumitories (including Yellow Corydalis) all produce capsules containing multiple seeds.

My copy of The Englishman's Flora (Geoffrey Grigson, Paladin) has no entry on Yellow Corydalis, but once again does discuss Common Fumitory. It seems there is some debate as to whether the name 'fumitory' refers to the pungent, eye-watering smoke that the plant supposedly emits when burnt, whether it is a reference to the 'smokey' colour of the foliage or whether it is a reference to the 'nitric-acid-fumes' smell of the roots. Referring to the second possibility, Grigson quotes William Coles' description of the foliage in his book Adam in Eden (1657) as

"a whitish blew colour as smoak is"

He also gives a rather nice quote from a Stockholm medical manuscript (c.1400)

"Fumiter is erbe, I say,
That springyth in April and in May
In feld, in town, in yerd and gate
There land is fat and good in state"

The poetry prize has to go to Jon Clare who (as I discovered from this site) writes:

"And Fumitory too, a name
Which superstition holds to fame,
Whose red and purple mottled flowers
Are dropped by maids in weeding hours,
To boil in water, milk, and whey,
For washes on a holiday,
To make their beauty fair and sleek,
And scare the tan from summer’s cheek"
(John Clare, quoted by Ann Pratt, ‘Wild Flowers’ (1857)

Can any maids out there report having tried this?!

Stinging nettle Urtica dioica

I am an amateur naturalist trying to learn a little about all the life in my garden.
In a quiet corner of my garden (at (1.8,2.0) - see here) I have been carefully cultivating (hem, hem) a patch of stinging nettles Urtica dioica (photo's 1 and 2 - click to enlarge).

I have two books in my possession that have enabled me to learn something about this ubiquitous British weed: my trusty copy of The Englishman's Flora (Geoffrey Grigson, Paladin) and secondly a recently acquired copy of Insects on Nettles (B.N.K. Davis, Richmond Publishing).

From Geoffrey Grigson's book I learn alternative names for the stinging nettle include The Devil's Leaf in Somerset and Naughty Man's Plaything (!) in Sussex. Secondly that nettles were unintentionally imported into the States by the settlers, with John Josselyn recording in 1672

"[nettles] have sprung up since the English planted and kept cattle in New England"

and thirdly that the Scots poet Thomas Campbell (1777-1844) wrote about sleeping in sheets made from the fibres of nettle stems (I would love to think there is someone out there reading this blog who still has a set of nettle bedsheets. If you're that slumberer do please leave a comment!)

From Dr.Davis' book I am learn that the botanical name dioica is derived from the Greek di-oikos -"two houses" - a reference to the fact that nettles have separate male and female plants which can be differentiated by the flowers: bright yellow on male plants and "silvery, furry" on females. Nettles clearly have a dubious reputation as a weed; Seen under the microscope however I have to say I find the flowers really rather beautiful. Photo 3 shows my 40x closeup of what I assume to be a female plant.

Nettle leaves are edible after suitable cooking (blanching in boiling water for example) and I can report that I myself have eaten nettle risotto from my garden's crop: my memory is of it tasting vaguely like a cross between watercress and spinach.

Of course, the unpleasantly familiar attribute of nettles is their sting. Photo 4 shows my (100x) image of one of the vicious hypodermic syringes responsible. It seems there is some dispute over exactly what chemical is to blame for the painful sting with hystamines, formic acid and oxalic acids all being variously implicated. Hope is at hand however: From Dr. Davis' fascinating book above I learn that one nettle variant (var. subinermis) common in Cambridgeshire lacks stinging hairs.

Nettles get a mention by Shakespeare no fewer than nine times, my favourite being

"the strawberry grows best underneath the nettle,
and wholesome berries thrive and ripen best
Neighboured by fruit of baser quality" (Henry V, Act 1)

Does anyone know if there is any truth in this suggestion that strawberries grow well in the proximity of nettles?

And finally, for all of us who've suffered the stings of nettles. I learn that things could be much worse: from Wikipedia's entry on nettles I learn that Urtica ferox, a dioica relative native to New Zealand, has a sting powerful enough to kill a horse! Can anyone out there report living to tell the tale of having been stung by this terrible triffid?

Rhubarb Rheum rhabarbarum

I am an amateur naturalist trying to learn something about everything living in my garden.

Situated in my garden border (at (0.6,1.0) - see here) is a patch of rhubarb I grew from seed some years ago. Frustratingly for the purposes of this blog, I have since lost the seed packet and can't remember the exact variety - there are dozens - though it may be Hawkes Champagne (is anyone out there expert enough to tell me from the photo's alone?).

Photo 2, which I took back at the start of May, shows a closeup of my rhubarb's flower stalk. For some reason I'd expected the flowers to smell unpleasant, but in fact they give off a sweet, heavy perfume and are very popular with pollinating insects.

Photo 3 shows the same flower heads some weeks after photo 2 was taken, now 'dripping' with red seed capsules.

I enjoy my rhubarb mainly for its architectural value in the flower bed, though I do occasionally cook some of the stalks. As everyone knows, rhubarb leaves are poisonous. They contain quantities of nasty chemical oxalates and (laxative) anthraquinone glycosides, and although (as I read here) you might need to eat a few kilogrammes to seriously risk death, eating far less would be enough to bring on some pretty unpleasant consequences.

By now, in my quest to discovery something about everything in my garden, I've learnt to expect everything I come across will have a long and remarkable history. Rhubarb certainly lives up to expectations! This site has answers to every rhubarb-related question I could imagine asking (and some I couldn't) and amongst other things I learn that rhubarb gets mentioned in Chinese herbals from 2700BC; that a general in the Ming Dynasty tried to commit suicide by overdosing on rhubarb medicine; and that the famous Marco Polo writes at length on rhubarb in his accounts of his travels. Rhubarb was being grown in Banbury, Oxfordshire (about 15miles from my house) "by Hayward" in 1777 for its herbal value. According to this site, the first English culinary recipe appeared in 1783 in John Farley's book 'The London Art of Cookery', and from the site of the Royal Horticultural Society I learn that in its heyday in the Victorian era, Yorkshire in the North of England was producing 5,000 tons annually. Rhubarb was imported into Maine in the US in the 1790's.

The UK's national collection is today held in the gardens at Harlow Carr. Now, I have nothing but respect for the botanical value of such collections, but I have to confess that the schoolboy in me can't restrain a titter when I bring to mind Python-esque phrases such as "The nation's rhubarb heritage".

Botanically, rhubarb is a member of the polygonaceae family of plants, comprising about a thousand species including sorrel and knotgrass.

Returning to the subject of my rhubarb's flowers, photo 4 shows a close up of a single flower (40x magnification). Rhubarb flowers have nine tiny white petals. In the centre of photo 4 you can see the threefold 'feathery' stigma, which sits atop the pistil - the female part of the plant. A grooved, waxy pollen-containing anther - part of the plant's male 'apparatus' - can be seen bottom, right-of-centre. Photo 5 is my photo of some rhubarb pollen. This site gives a detailed botanical description of the polygonaceae and contains a link to labelled botanical drawings of rhubarb flowers.

And finally, in preparing for this posting I was delighted to discover that Ulm, Montana hosts a rhubarb festival . My imagination runs wild! If you're reading this and have attended, please leave a comment to let me just what it is that goes on at a festival of rhubarb!