XII. LICHENES. 



945 



the same way as in Hehellew, Pezizm and most Fungi of the group of Ascophoreoe. 

 At germination the spores of Lichens produce, like Eungi, a net-work of 

 filaments. 



The spermogonia are small conceptacles immersed in the superficial layers of the 

 thallus, rarely placed in distinct tubercles, communicating with the oiitside by a 

 small orifice, and containing simple or jointed filaments {sterigmata), which pro- 

 duce small arched oblong linear or acicular corpuscules {sperinatia), the supposed 

 fertilizing agents. The spermatia are of extreme tenuity ; the largest are -00048 to 

 ■00067 in., the smallest -00003 in. in length, with half that breadth; they do not 

 appear to have any power of motion, and possess no locomotive organ. Although 

 lichenists are agreed in considering the spermatia as the analogues of the anthero- 

 zoids, it is difficult to describe their action on the spores. It has been observed in 

 certain genera that some individuals of a species have spermogonia, others not ; 

 whence it would appear that such species are dioecious, and not monoecious, like 

 most Lichens. The genus Ephebe is an example, the species of which may be 

 considered as monoecious or dioecious, according as the spermogonia and apothecia 

 are found on the same or on different individuals. 



Pycnidia are small conceptacular protuberances, resembling spermogonia, but 

 differing in their less abundant, more bulky contents, and in their germinating 

 power. Their origin and functions are still quite obscure. Tulasne considers them 

 to be a supplementary means of propagation. 



Nylander, from whom we have adopted most of the preceding views, has divided 

 Lichens into several families, which, in our opinion, represent tribes, and form the 

 three following very unequal groups as regards the number of genera which they 

 contain : 1 . Collemacew, with fifteen genera ; 2. Myriangiacew, with one, Myriangium; 

 3. LichinacecB proper, which contains a hundred. 



Gonionema. 

 Paulia. 



Tribe I. COLLEMACEW. 



Synalyssis. 

 Obryzum. 



Leptogium. 

 Ephebe. 



Spilonema. 

 Oollema, &c. 



Tribe II. MTBIANGIACEjE. 



Myriangium. 



Tribe III. LICHINACEJE p-roveb.. 

 Section I^ Bpiconiode^. 



Calycium. Coniocybe. Sphserophoron. Acroscyphus. 



Section II. Cladoniode^. 



Bceomyces. Oladonia. Stereocaulon. 



Section III. Eamalode^. 



Roccella. 

 Evernia. 



Siphula. 

 Bamalina. 



Usnea. 

 Cetraria. 



Alectoria. 



3p 



