The English flora - SeaweedAfrica

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•204 L1CHENES. [Sticia.
Stones and walls, rarely on trees in Scotland, but not general : and
always barren.
29. P. parietina, Ach. {yellow wall Parmelia); thallus orbicular
brigbt-yellow the lobes marginal radiating appressed
rounded crenate and crisped granulated in the centre, beneath
paler and fibrillose, apothecia deep-orange concave with an entire
border.—Ach. Syn. p. 200. Lichen parwtifms, Linn.—E.
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Bot. t. 194.—Dill. Muse. t. 24. f. 76.
On trees and walls, abundant.
** Thallus with its segments inflated at the extremity.
30. P. physodes, Ach. {inflated Parmelia); thallus orbicular
stellated glaucous-white the segments sinuato-multifid convex
glabrous inflated often bearing elevated powdery warts, beneath
brownish-black, apothecia red-brown with a thin elevated border.
Ach. Syn. p. 218. Lichen physodes, Linn—E. Bot.
t. 126.—Dill. Muse. t. 20. /. 49.
Trunks of trees, stones, and low bushes, not unfrequent.
very rare : on an ash-tree, near Dumfries, Dr. Richardson.
Apothecia
31. P. diatrypa, Ach. {double-coated Parmelia) ; thallus substellate
greenish-grey, the segments sinuato-multifid nearly plane
smooth bearing powdery warts and perforated the extremities
inflated, apothecia reddish-brown the border inflexed entire
Ach. Syn. p. 219. Lichen diatrypus, Ach. Prodr.—E. Bot.
t. 1248.
Wet rocks, among moss, rare. Foot of Snowdon, Mr. D. Turner.
At Ballacheulish, bearing apothecia, Turner and Hook.— Smaller than
the last, with narrower segments ; forming, however, with it, a small but
natural groupe of the Genus, distinguished by the thallus, especially at
the extremity, being hollow and having a distinct upper and lower membrane.
The P. enteromorpha, from the N. W. Coast of America, is a
still more remarkable example of this tribe.
19. Sticta. Ach. Sticta.
Thallus foliaceous, coriaceo-cartilaginous, spreading, lobed,
free and downy beneath, with little cavities or Iwllow spots
{cyphellai) often containing a powrdery substance. Apothecia
{scutellce) beneath formed of the thcdliis, to Avhich they are appressed
and fixed by a central point, the disk coloured, plane,
surrounded by an elevated border formed of the thallus.—Name;
(jtizto;, dotted, from the depressed spots, or cyphellce, with which
the under-side of the thallus is dotted ; and which is indeed the
only technical character by which the Genus is distinguished
from Parmelia.
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" These," Mr. Borrer observes, " vary much
in their nature : in a few species they are merely irregular bald
spots, apparently proceeding from abrasion of the surface ; in
others, they are powdery warts, soredia, without a margin ;
and
again, in others, as in S. macrophylla, little pits {cyphellcE,) furnished
with a margin from the superficial membrane of the thallus
within which they are originally formed : these cyphellce also