Didymodon icmadophilus again

H and I came across an interesting Didymodon while walking along the Abergarwed Forest road on Sunday. It appears to be identical to the Didymodon icmadophilus found by Barry in Aberpergwm. The Abergarwed population was growing in a typical forest road community which included Cratoneuron filicinum, D. fallax and D. ferrugineus among others. 

Didymodon icmadophilus, in fine gravel Abergarwed Forest road

The Abergarwed plants share the key features shown by the Aberpergwm plants, i.e. the strikingly attenuated leaf tip made up mostly of costa and the quadrate (rather than rounded) papillose leaf cells.

Attenuated leaf tip of the Abergarwed D. icmadophilus

Quadrate, papillose leaf cells of the Abergarwed D. icmadophilus

I can't help thinking that I have seen plants like this before on forest roads which I have either ignored or passed over as odd looking D. rigidulus. Barry has drawn our attention to the current taxonomic confusion with this 'species' which may be absorbed into D. acutus. In the Flora of North America it is named D. rigidulus var. icmadophilus which, however, is described as having non-papillose cells. Our plants seem to be more similar to the taxon named D. rigidulus var. gracilis which is also described in that flora. Smith mentions D. acutus var. icmadophilus and D. rigidulus var. icmadophilus as former names.

This is an interesting addition to the bryophyte flora of forest roads in south Wales and I suspect that it is widespread in small and easily overlooked populations. Until its taxonomy is sorted, and if everybody agrees,  I suggest that we record plants that fit this description as Didymodon icmadophilus.