H2 LICHENES. [Parmelia. 



expand into new fronds. Varieties occur with the pruina very indis- 

 tinct on the thallus, and sometimes altogether wanting from the disk of 

 the apothecia. 



4. P. stellaris, Ach. Thallus stellate, of a pale glaucous- 

 grey, little changed when wet, with crowded, minute, white, 

 subconfiuent spots, at length wrinkled, white beneath, with grey 

 fibres; the segments linear, rather convex, multifid ; apothecia 

 with a black disk ; the border at length waved and crenate. 

 Ach. L. Un.p. 476. Eng. Bot. t. 1697. 



On trees and on stones ; common. The pale whitish spots become, 

 in very old plants, at first rotund solid granulations, which at length 

 expand into new fronds. A pruina is sometimes observable on the disk 

 of the apothecia. 



2. Buds granulate. 



5. P. plumbea, Ach. Thallus stellate, greyish-lead-coloured 

 or greenish-grey, beneath thickly tomentose of an azure black, 

 segments ad pressed ; their edges elevated, crenulate ; buds in 

 central grey granulations ; apothecia central, often crowded, 

 flattish ; their disk brown ; their border at length crenulate. 

 Ach. L. Un. p. 466. Eng. Bot. t. 353. /3. affinis. the border 

 of the apothecia thick, elevated, inflexed, crenated. Parmelia 

 rubiginosa, and P. conoplea, Ach. L. Un. p. 467. Lichen 

 affinis, Dicks. Cr. Fuse. 4, p. 24, t. 12, f. 6. Eng. Bot. t. 

 983. 7. tumescens, thallus bluish-grey, thick and tufted in the 

 centre ; segments at the periphery minute ; apothecia very con- 

 cave. B. microphi/lla. thallus very minute. Lee. microphylla 

 var. thriptophylla Ach. Syn. p. 58. 



«, and 3, usually growing together on the same trees ; common ; 7. on 

 rocks, at Blackwater, County of Kerry. S. on rocks. Whenever buds 

 occur on the thallus of any of the Parmelice, they are almost always 

 likewise found on the backs and edges of the apothecia, and give these 

 a new character. When granulations, in the present species, are ab- 

 sent, the margins of the apothecia, though waved, yet for the most part 

 remain entire ; constituting the P. plumbea of Acharius ; when present, 

 reappearing on the margins of the apothecia, they give to the edges a 

 thick, elevated, crenate appearance constituting the P. rubiginosa of the 

 same author. In the first case, (such is the liability of the apothecia 

 to change their habit) I have observed, on the same thallus towards the 

 edges, the shields with a perfectly thallodal margin of a greyish lead 

 colour, and towards the centre quite black as well as the disk : in both 

 cases spongy fibres proceeding from the backs and bases of the apo- 

 thecia attached themselves to the thallus, giving an additional testimony 

 to the thallodal nature of the margins of the apothecia. The variety 7. 

 which I had at first taken for a distinct species, is very remarkable for 

 its greyish-blue colour, its edges are thin and adpressed to the rock, 

 while the centre is elevated more than one-fourth of an inch into a 

 cushion consisting of coarse granulations, which at length assume 

 white edges and become flattened, and among which the concave apo- 

 thecia with crenate borders, are partially immersed. This I have traced 

 by intermediate states to the variety 3. At Cromaglown, Kerry, we 



