Plants of Skye, Raasay & The Small Isles

A few years ago I wrote a short note about Sex Change in Trees. Today I have spotted another example of environmental sex determination, this time in Acer pensylvanicum (Striped Maple). Apparently, these trees increasingly flower as females as their health deteriorates.

A recent paper looking at underlying mechanisms “demonstrates that physical trauma in striped maple appears to exhibit a threshold effect in which only the most stressful of physiological cues instigate changes in sex expression …. and that damage stress is strongly correlated with switching to femaleness. ”

Nowt so queer as trees.

Neil has sent me a couple of records from February including this nice patch of Hymenophyllum tunbrigense (Tunbridge Filmy-fern) from the Drinan area – the first record in NG51 since 1995 and in pretty much the same place as one of the two records made then.

Hymenophyllum tunbrigense (Tunbridge Filmy-fern)      Photo: N. Roberts

Note the teeth on the indusia  – the cover of the sori which contain the sporangia, the spore-bearing structures. This is the best way to distinguish it from the locally common Hymenophyllum wilsonii (Wilson’s Filmy-fern).

If you struggle with sundews, particularly Drosera intermedia (Oblong-leaved Sundew) and Drosera x obovata (Obovate Sundew (D. rotundifolia x anglica)) there is a useful new guide here.

Drosera intermedia has, in my opinion, been over-recorded in the past in our area.

(N.B. Ignoring a very small number of dubious records,  Drosera x belezeana (D. rotundifolia x intermedia) is known only from a small area in the extreme south of England.)