Thursday, August 2, 2007

Barren Brome Bromus Sterilis

I am an amateur naturalist attempting to identify every living creature in my garden.

The wonderful thing about being an amateur is that you get to discover so much. For example, in preparing for this posting I have made the astonishing discovery that grass is a flowering plant! Hitherto, I have to say I had assumed that flowering plants had obvious flowers, and that grass was...er, well... green stuff. I confess, I do have a suspicion that the botanical community might just have beaten me to my discovery!

Until recently you could find a clump of grass growing in my garden at (0.6,0.8) (see here). I say 'until recently' as my grass is an annual: the photo left (click on photos to enlarge) was taken back in May. Having set seed, the clump has since died back.

Photo 2 gives a clearer view of one stem. Botanists refer to the "busy area" at the top of the stalk (the 'culm') by the lovely name "a nodding panicle".

According to my copy of Grasses (Hawley, Shire Nat. Hist.), more than 150 species of grass grow in Britain. So, how do you set about identifying the species of the one you happen to be looking at? Answer: first, find your ligule! No, prior to my preparation for this posting, I didn't know what a ligule was either. A ligule, it turns out, is a small, semi-translucent, vestigial leaf-like structure that sits at the junction between the stem and each of the leaves. You can see one in photo 3 (the little white pointy thing). It turns out that the nature of the ligule (pointed or blunt; ragged or smooth; present or absent etc.) is a useful species clue. Others include the presence or absence of hairs on leaves or stem, the dimensions of leaves and stem, and of course the nature of the panicle (for example, in some grasses, a compact spike; in others, as here, a nodding panicle).

Noting the hairless stems, downy leaves, pointed ligule, the purplish colour of the lower culm and various other features, and working with my copy of Grasses (Fitter,Fitter,Ferrer; Collins pocket guide), and the photo's in Grasses,Ferns, Mosses and Lichens (Roger Phillips, Pan Books) I'm fairly confident in identifying my grass as Barren Brome (Bromus sterilis).

Returning to the issue of grasses being flowering plants mentioned in the first paragraph, photo 4 shows a closeup of one of my grass's spikelets. The spikelets are, in a sense, the rather complex flower-heads of grasses. There is a complex set of terms (awns; lemmas; glumes and paleas to name a few) that identify all the various parts of a spikelet. The awns, for example, are the long bristles seen in the photo emerging from the ends of the spiklet. Hidden amongst the complexity of the spikelet are the tiny pollen-bearing (hay-fever causing!) anthers and female ovaries of the grass, that make up a grass flower. I have not gone to the trouble of dissecting out and photogrpahing all these various parts, but it is something I hope to return to in a future posting.

Finally, regular readers will know I'm fond of viewing things under my microscope. Clicking on the photo above to enlarge you'll note the presence of a number of tiny grass seeds. Photo 5 shows two viewed at 40x magnification. I'm intrigued by the seeds' concave 'boat-like' shape and wonder what purpose it serves for them to be shaped like this. I've read that some plant seeds are cleverly shaped so that, when lying on the soil, if they are subjected to random 'jostling' (say, by a passing breeze) they act like little corkscrews and quite literally drill themselves down into the soil. I wonder whether the shape of my grass seeds indicates they are of this type. On the other hand the explanation might be something else entirely. If anyone out there happens to know, do please leave a comment.

2 comments:

Gaye from the Hunter said...

hi Henry,

I am extremely pleased to have found your blog. It appears that you and I are on the same journey - both amateur nature enthusiasts attempting to teach ourselves about the intricacies of nature that we are sharing our living space with.

I am envious of the books available to you - I'd be like a pig in mud if I had such books to consult.

Recognising native grasses vs introduced grasses is one of my near future projects. I live in a rural area of the Hunter Valley in NSW Australia where agriculture has seen the introduction of much green stuff. Perhaps some of the grasses that escape council slashing on roadside verges are native, but I have no idea. I wish to grow some native grasses to attract finches and other gound-feeding birds to my yard.

I will be a regular visitor to your blog, and will place a link to your blog on my site.

Regards
Gaye

Henry Walloon said...

Gaye,

Yes, I do tend to gather rather a lot of books. For our little wet island over here, there's generally at least one fairly comprehensive account of most aspects of our natural history. For a continent the size of Oz (do I recall reading that a whole new tree species was discovered there only a few years ago ?!) I guess things may be a little more tricky!

Thanks for the encouraging words.
I'll be visiting your site frequently also.

Henry