Friday, 27 January 2017

Didymodon sinuosus oddities

I'm pretty familiar with Didymodon sinuosus now, and probably see it in the majority of tetrads I visit in SE Glamorgan, but have recently come across a couple of odd examples of what I think can only be this species.

The first was on limestone rubble in secondary woodland near Wenvoe garden centre on 22nd January. The plants were dry and shrivelled so I took a sample home to confirm the ID, and on moistening it became obvious that a couple of the older leaves had clusters of filamentous gemmae along the costa. I'm afraid the photos are not the best, see below.

I can't find any mention of gemmae in this species, except for a fairly recent reference to protonemal gemmae in Rare and Interesting No. 11. This reference also mentions that "Correns (1899) had reported gemmae from a Sussex plant in the late 1880s", but doesn't say whether these were protonemal or not. Has anyone else seen similar plants?

The following day, I collected a very shiny-leaved sample from Llanilid Churchyard. I didn't even suspect this was D. sinuosus, which is usually much more opaque-looking, but having checked it microscopically I think it must be. The leaf cells are not at all papillose, even near the leaf tips, but otherwise they look spot on for D. sinuosus with their wavy, notched margins. Smith mentions that the cells are papillose in this species, which fits with the opaque plants I'm faimilar with. I guess this is just natural variation; many of the Didymodon species seem to vary in the degree of 'papillosity' of their cells.

Any comments welcome, thanks.


  1. Never seen anything remotely resembling your gemmiferous plants - quite extraordinary! Not sure about your shiny plants? I thought I'd reached a level of familiarity with our Didymodon spp., but all of these weird forms are dampening my confidence.

  2. I've never seen gemmae on the leaves of D. sinuosus. Also, gemmae in Didymodon are usually spherical or elliptical aren't they? All the populations of D. sinuosus I've seen have at least some plants with leaf tips missing - deciduous leaf tips are an important means of propagation for this species which in the UK is entirely composed of female plants. Could your plants be Orthotrichum lyellii which does sometimes (albeit rarely) grow on rock?

  3. That's an interesting thought Charles, but what's not shown in my poor photos is that some of the leaf tips are missing and the leaves have the wavy, notched margins typical of sinuosus. In all other respects they look typical sinuosus. But those gemmae really are weird!

  4. In the Bryophytes of Cornwall, Holyoak makes mention of a specimen with foliar gemmae

  5. Thanks very much Graham - I'm in touch with David Holyoak re Cornish bryo records so I'll send him my photos and see what he thinks.