|l ACOTYLEDONS. — LICHENS. Tkclotrema. 45 



Hab. On rocks with the preceding, Lightf. Common. 



Sir James Smith justly remarks, that this seems to unite the foregoing 

 and the following species. 



7. E. IVeberi, thallus cartilagineo-coriaceons Inbed greenish 

 brown olivaceous beneatli raCner tawny or blackish on both 

 sides smooth, tlie lobes laciniated waved ])laited and crisped 

 crowded, orifices rather convex black. Ach. Syn. L'lch.p. 103. 

 Lichen aqiiaticus, E. B. t. .594. 



H.^B. Rocks and stones over whicli v/ater trickles, within reach of the 

 spray of cascades, &c., not uncommon. 



Div. II. CcENOTHALAMi. Licliens ivkose apotliec'ia arefor77i- 

 ed in part from the substaiice of the crust or thallus. 



Sect. I. Phymatoidei. Apothecia includedin wart-like pro- 

 cesses which are formed of the thallus. 



11. PORINA. . 



Universal receptacle crustaceo-cartilaginous, expanded, plane, 

 aduate, uniform, with wart-like processes. Partial receptacle 

 immarginate (1 or more), hid within the substance of the 

 wart, and surrounded by a very thin diaphanous membrane, 

 its orifice thicker coloured, in the surface of the wart, and 

 containing a §ubglobose cellular nucleus. 



1. P. pertusa, crust smooth even whitish grey, warts of the 

 apothecia subglobose, orifices many depressed black. Ach. 

 Syn. Lich. p. \09. Lichen pertusus^ Light/, p. S02. E. B. 

 t. ()77. 



Hab. Trunks of trees and sometimes rocks, Lightf. 

 12. THELOTREMA. 



UwwersaZrccep/flc/e crustaceo- cartilaginous, spreading, plane, ad- 

 nate, imiform, with wart-like processes, perforated with a wide 

 pore, and margined. Partial receptacle solitary, included 

 in the wart, with a double coat; one dimidiate, superior, 

 thick (black), rarely wanting ; the other very thin, membra- 

 nous, sometimes breaking above, inclosing a compressed cel- 

 lular nucleus placerl in the bottom of the wart. 



1. Th. lepadimim, crust smooth whitish, warts of the apothecia 

 smooth somewhat cone-shaped with the margin of the aper- 

 ture thin simple somewhat indexed and contracted covered at 

 the bottom with a membrane which bursts. Ach, Syn, Lich. 

 p. 115. Lichen inclusus, E. B. t. 678. 



Hab. On the bark of Hex aquifolia, at Bilston-burn, near Edinb.^ 

 Mr. G. Don. 



2. Th. exanthematicum, crust siibtartareous thin contiguous 



