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sum(score * weight) /
(total weight + 1)
to a paper having the “checklist” of species of lichens for this location. The Physconia spp. are:
P. distorta (=P. pulverulenta), P. enteroxantha, P. muscigena v. bayeri, P. perisidiosa, P. servitii, P. subpulverulenta, P. venusta.
My concern is that these specimens are not only pale near the margin, they are entirely white even toward the center (although the black rhizines tend to obscure this fact).
Yes, you’re right, P. grisea also does this, and lack of soredia could definitely just be age. The rhizines (at least the outer ones which aren’t obscured) are nearly all simple, also good. But I do see a few starting to become squarrose (at the top) and they are all, even the young rhizines, distinctly black. British Flora says they should be pale to at most brown. So I’m still skeptical.
P. perisidiosa not only is black toward the center, it is decorticate toward the lobe tips causing the lobes typically to curl up a bit. But if the specimen is too young to develop soredia yet, then you won’t see this.
P. muscigena also blackens toward the center. The ones I’ve seen have a distinctive loosely-overlapping, matted growth habit. It is typically on moss as the name implies. It is rarely fertile. Maybe, but it still seems a stretch to me.
This location must have been an excellent study for Physconia. Maybe there’s an undescribed species hiding in all these details that don’t quite match up?
I’m “young” in Physconia. Let me try to explain, in a few steps:
1) In this recent “expedition” to this big location I saw “hundreds” of specimens of Physconia, but not all of them are P. venusta, though this is perhaps the most common species here;
2) Beyond P. venusta, not all Physconia spp. have dark underside;
3) In the site AFL the following statements concerning the underside are made:
Physconia perisidiosa:“Face inférieure brun sombre vers le centre, plus pâle vers la marge, dépourvue de cortex vers la marge ; rhizines noires, allongées, fortement pénicillées (parfois simples à la marge)”.
Physconia grisea: “Face inférieure presque blanche avec des rhizines simples (le seul Physconia à rhizines simples)”.
4) For Physconia muscigena in CNALH it is written:“lower surface: pale or darker brown on the peripheral lobes, darkening to black inwardly, dull to weakly shiny; rhizines: black, mostly squarrosely branched”.
5) Can’t the specimens in observation 92533 and observation 92534 belong to P. muscigena?
6) The lack of soredia of the specimen in observation 92533 can be due to youngness? If so, can’t it be P. grisea?
For the purpose of comparision of Observations I upload a photo.
Again: not sorediate and white underneath?
Created: 2012-04-11 20:18:59 CDT (-0400)
Last modified: 2012-04-11 20:19:00 CDT (-0400)
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