94 LICHENS. 



of the trees upon which they grow ; while the fructi- 

 fication is very minute, forming little black streaks 

 or lireVla (lira, a furrow), irregularly arranged, and 

 resembling somewhat the letters of some of the Ori- 

 ental alphabets. 



In Gr aphis script a (fig. 26) the thallus is thin, 

 somewhat membranous, smoothish, shining, greyish 

 white, and faintly bordered with black. The lirellse 

 (fig. 27) are partly sunk in the bark, winding and 

 narrow, some being simple, others branched; and 

 they are surrounded by a raised border, formed by 

 the thallus. The lirellse are lined at the sides with 

 a black (carbonaceous) layer or excip'ulum, within 

 which are situated the asci and paraphyses. The 

 spores (PL II. fig. 29) are 8-cleft, the segments being 

 again divided longitudinally into little spores or 

 sporidia. 



In Opegrapha betulina (PL II. fig. 30), which is 

 found on the bark of the birch-tree, the thallus is 

 thin, dirty yellowish white, bordered with black. The 

 lirellse (figs. 31, 32) are mostly simple, without a 

 raised border of the thallus, and the excipulum forms 

 a complete lining to them. The spores (fig. 33 a] are 

 3-cleft, and taper at the ends. 



CALICI'EJE. Calidium claveVlum (PL II. fig. 6) is 

 a pretty little Lichen, growing upon old boards and 

 farm-buildings. The thallus is granular and greyish 

 white. The apothecia (fig. 7) are stalked and black, 

 but of a lighter colour than the mass of spores form- 

 ing the nucleus. The spores are very minute, black, 

 oblong, and divided by a transverse septum. 



The Lichens are divided into two Orders, according 

 to whether the apothecia are open before the spores 

 are ripe, as in the species noticed above, or whether 

 the apothecia only open to discharge the ripe spores. 

 The first Order forms the Gymnocar'pi (yt>/-tvo?, naked, 

 /capTrbs, fruit) ; the second forms the Angiocar'pi (dy- 

 yeiov, vessel, capsule). 



