Sunday, February 3, 2008

Soft-tufted Beard Moss Didymodon (Barbula) vinealis

I am an amateur naturalist trying to identify all the lifeforms in my garden.

Growing on a stone next to my vegetable patch (at (0.2,1.6) - see here) is the moss seen in photo 1 (click photo's to enlarge).

For this posting I was fortunate enough to gain access to a low power stereo dissecting microscope. My usual technique of balancing my cheap digital camera on the eyepiece didn't deliver such good results as it does with my own higher-power microscope, but the stereo' did allow me to capture some photo's at 16x magnification of the moss in its wet state (photo 2) and (photo 3) the remarkable 'twisted-rope' structure the leaves adopt if the moss is left to dry out. Mosses are able to withstand considerable drying incidentally, all that's needed to bring them back to full greeness being a few drops of water.

Previously, I've talked at length (here, here and here) about some of the features to look for when identifying mosses. For this posting, suffice to say that the combination of elongated leaves with their circular cells and nerve running their full length, together with a few other features and reference to my copy of British Mosses and Liverworts (Watson, Cambridge) and a recently acquired copy of The Moss Flora of Britain and Ireland (Smith, Cambridge), leads me to conclude I've got Didymodon (Barbula) vinealis growing in my garden (though as always, my identifications come with a 'health warning' - I'm always happy to be corrected). The website of the British Bryological Society gives the common name as Soft-tufted Beard Moss.

Though I realise the following will be decidedly 'old news' to the experts out there, I can't end today's posting without relaying a fascinating feature of mosses that I discovered recently from leafing through some botany textbooks. As most people know, DNA inside living cells gets packaged up into chromosomes. Human cells contain 2 sets of 23 chromosomes (i.e. 46 in all) and are said to be diploid. The exceptions are sperm and eggs; These contain only 1 set of (23) chromosomes and are said to be haploid. This pattern is common across almost all mammals. Mosses do things differently however; When you look at a moss you are seeing a mass of haploid cells, except, however, where you see stalk-like setae (you can see a number in photo 1. Photo 4 shows a closeup). These are the a moss's spore-filled fruits. In contrast to the rest of the moss, the cells comprising the setae are diploid. In a sense therefore, your or my diploid arms 'sprouting' from our diploid torsos, are a genetically 'closer match', than a moss's diploid setae sprouting from its haploid host.

There are more things in heaven and earth, Horatio, than are dreamt of in your philosphy!


R2K said...

Great work as always : )

Henry Walloon said...

Thanks for the encouragment r2k - a pleasure to see you here as always