"Definitely Rather Ambiguous"

A couple of weeks back I was wandering up the edge of a ravine when I spied a small cluster of Maidenhair Spleenworts growing out of a natural rockface. Something about them struck me as being odd, though I wasn't sure quite what. Through a handlens I quickly realised that each pinna was attached to the rachis from a more or less central point, the overall impression being that the pinnae were diagonally inserted. Here are a couple of pics, taken at the time. 

Note that the tiny 'stalk' on each pinna is more-or-less centrally placed on the leaf lobe

There are three subspecies of Maidenhair Spleenwort native to Britain. By far the commonest subspecies, Asplenium trichomanes quadrivalens, occurs across most of Britain and has the pinnae attachment point at the very bottom corner of the leaf lobe.

Asplenium trichomanes pachyrachis appears to be a genuinely rare plant in Britain and is restricted to a handful of limestone areas. The third subspecies is Asplenium trichomanes trichomanes, which occurs on acidic rocks and is scattered throughout Britain, including Scotland. Both of the latter have the pinnae attached more or less centrally, a bit like my plants did. I felt relatively confident that I had a non-quadrivalens plant on my hands and a look at the distribution maps pointed to it being subspecies trichomanes, which would be a not-entirely-unexpected addition to the flora of Skye. Cool beans. 

All three subspecies show a degree of morphological variability and the surest way of distinguishing one from the others is to measure the size of the spores and stomata - something beyond my abilities (I really must get a measuring graticule some day!) I asked for help. 

I went to Stephen Bungard, VCR for Skye, who in turn went to local fern expert James Merryweather, who in turn went to distinguished pteridologist Roger Golding. I was included in the email thread and was encouraged to see Roger state: 

It looks reasonably good for subsp. trichomanes. The overall habit and appearance, and specifics like the diagonal insertion point of the pinnules and strongly marked ridges on the upper surface of the pinnules, all suggest subsp. trichomanes. There are rather more than typical number of sori per pinnule (most plants of subsp. trichomanes have 3 pairs or fewer on the majority of pinnules, but some plants do have more). I would hesitate to say definitely from photographs - technical confirmation via measurements of spores and/or stomata is always good where an element of doubt exists (I’m happy to do that if anyone wants to send me fronds).

Next step was to send Roger some samples. I returned to the site, collected a dozen or so fronds from two different colonies of plants, kept a few back for myself, and posted the rest off to England. Here are a few more pics, taken on my second visit

General habbo pics and one showing reduced number of sori - hopefully indicative of A.t.trichomanes

I shared those images with Roger who replied:

Looks interesting. The presence of Polystichum aculeatum suggests a more basic soil/rock, where you are more likely to find A. t. quadrivalens. But Aspleniums can live in the humus layer on top which may be more acidic. Anyway, will be good to check out the fronds.

The fronds in question duly arrived and today Roger came back to me with his verdict:

I have checked these now and they are both quadrivalens. Morphologically I was not at all sure when I took them out of the packages - they are definitely rather ambiguous with some features that could be interpreted either way. Even the spore size was rather ambiguous: average 33.28 for the South sample and 33.78 for the North sample. This is at the bottom of the range for A.t.q and not far off the top of the range for A.t.t. However, fortunately the stomata measurements are unambiguously in the tetraploid range so they must be quadrivalens. Happy to look at any more samples. I would be surprised if subsp. trichomanes does not occur somewhere on Skye. It’s certainly under-recorded nationally.

Well that's a pity. But, if nothing else, it shows that A.t. quadrivalens is quite a variable beast which is good to know and, best of all, I have a very competent pteridologist who is happy to check anything else I might get stuck with. As the saying goes, every cloud has a silver lining (and let's face it, there are generally lots of clouds on Skye!)

It turned cold here last night, the wind shifted to a northerly and I (briefly) contemplated closing my window. The local weather forecast is saying that, factoring in the windchill, we're in for almost a solid week's worth of minus figures. It does suggest that the temperature may rise to the heady heights of one degree later this week, but only for an hour or so. I opened the door earlier to find myself in a swirling mass of hail. From the warmest New Year's Day on record to swirling hail in a little over 48 hours, tis odd times we're experiencing folks. 

Luckily, I have just the song to take your mind off all that stuff. Sit back and chill to the sound of Ramrod singing Leda. This brother and sister fronted Italian band is generally a little bluesy for my liking, but they've thrown in a bit of mysticism to a few tracks, including this one, and have now created their own sound. This is from their 2019 album Jet Black which I'd definitely recommend giving a listen, particularly if you like your bluesy stuff with a twist.