232 LICHEN ACEI. [EVERNTA. 
Form 3. ceratea Nyl. Lich. Scand. (1861) p. 73.—Thallus de- 
eumbent; lacinie narrow, convex and subcylindrical, acuminate, 
subglabrous.—Cromb, Grevillea, vi. p. 21.—Parmelia furfuracea 
f. ceratea, Ach. Meth. (1803) p. 255.—Brit. Evs.: Cromb. n. 139. 
Distinguished by the form of the more naked laciniz ; but intermediate 
states occur, in which these characters are less marked, With us it is 
always barren, though Acharius (Lich. Univ. p. 501) says the apothecia 
chiefly occur in this form. 
Hab. On rocks and old walls in upland distriets.—Distr. Seen only 
from a few localities in 8.W., Central, and N. England, 8. and N.E. 
Scotland, and the 8.W. Highlands.—B. M.: Hunter Tor, Dartmoor, 
Devonshire ; Helminton, Cornwall; near Buxton, Derbyshire; Winder- 
mere, Westmoreland; Alston, Cumberland. Pentland Hills, near Edin- 
burgh; Glen Falloch, Perthshire; Deerhill Wood, Forfarshire; near 
Countesswells, Aberdeen. 
42, PARMELIA Ach. Meth. (1803) p. 153 pro parte; Nyl. Syn. 
i. (1860) p. 375.—Thallus foliaceous, horizontally expanded or 
rarely ascending, variously 
lobed and laciniate; epi- 
thallus somewhat shining, 
beneath usually  fibrilloso- 
rhizinose; medullary layer 
woolly, composed of fila- 
ments loosely interwoven ; 
cortical layer thin, formed 
of minute cells with thick- 
ened walls. Apothecia scat- 
tered, scutelliform, with thal- 
line margin; hypothecium \ 
colourless, thece short, the 
wall thickened above ; spores c 
usually 8n, ellipsoid, simple, 
colourless ; hymental gelatine b 
bluish with iodine. Spermo- 
gones generally scattered, Ss 
at length slightly prominent, <> (Ge 
blackish; sterigmata 2-5- 
articulate; spermatia acicular, Was.et © 
fusiformi-incrassate at either Fig. 44. 
apex. 
Parmelia periata Ach.--a, Fragment of the 
! if f 
The species vary i . thalamium and a theca, x 350. _O. Three 
but oe be the Bee) ee spores, X500. c. Vertical section of the 
ontally expanded a aie thallus, with two spermogones, x 80. 
Fouecils Fo P Tn eo i he a et d. pienemsle and ea x 500. 
or: ‘i . Three gonidia, 50. 
are the reactions of more value“ eee e 
in discriminating species, which were often not distinguished from 
each other, or were regarded merely as varieties, forms, and states, 
) 8 yy ) ) 
