Parmelia.] LICHENBS. 141 



f f f Thallus foliaceouSf or membranaceous. 



25. PARMELIA, Ach. 



Thallus foliaceous or membranaceous, stellato-lobate, or laci- 

 niated; apothecia orbiculate, sessile or substipulate, exte- 

 riorly as well as the margins formed of the thallus ; the disk 

 concave, coloured. 



In the following arrangement, particular attention has been paid to 

 the figure and situation of the buds, or those powdery collections, the 

 parts of which, in almost every species, have been observed to expand 

 into perfect individuals. In practice they are found to be more dis- 

 tinctive than the apothecia. The Genus Borrera, Ach. would have been 

 most gladly retained if any solid character existed by which it could 

 be separated from Parmelia. 



* Extremities of the lobes uninflated. 

 1. Buds indistinct. 



1. P. parietina, ACH. Thallus orbicular, yellow, pale be- 

 neath ; the lobes flattish, dilated at the top, rounded, subcre- 

 nate ; apothecia central ; their disk dark orange ; their border 

 entire. Ach. L. Un. p. 463. Eng. Bot. t. 194. 



On old fruit trees, and on others ; also on rocks ; common. This 

 is unlike any other Irish Parmelia. I can find no satisfactory distinc- 

 tions between it and that variety of Lecanora candelaria called 

 polycarpa. 



2. P. herbacea, ACH. Thallus orbicular, smooth, whitish- 

 brown when dry, greenish when wet, pale and tomentose be- 

 neath ; lobes incised, rotundato-laciniate, subcrenate ; apothecia 

 at first globular, projecting beneath as well as above the frond, 

 at length sessile ; their disk reddish-brown ; their margins ru- 

 goso-crenate ; their backs wrinkled. Ach. L. U. p- 459. Lich. 

 l(Btevirens, Eng. Bot. t. 294. P. alomulifera, Ach. L. Un. p. 

 456. Eng. Bot. t. 293. 



On old trees, also on rocks, in woods ; common. This would range 

 better under Sticta than Parmelia, and is at any rate a completely con- 

 necting link. The glomeruli on P. glomulifera, Ach. appear to be pa- 

 rasitic, and in the absence of any other character are quite insufficient 

 to constitute a distinct species. 



3. P. pulverulenta, ACH. Thallus stellate, brownish-grey, 

 pruinose when dry, glaucous-greenish-grey when wet, with 

 dark thick fibres beneath ; the lacinitz linear, multifid, flattish, 

 waved ; apothecia central ; their disk blackish, pruinose ; their 

 border thick, entire, inflexed, at length flexuose. Ach. L. Un. 

 p. 473. Eng. Bot. t. 2063. 



On trees ; common. The buds probably are those granulations of 

 the edges and surface of the old thallus, which flatten, and at length 



