FLWGI 



319 



By far the greater number of lichen-forming fungi are Discomycetes 

 or Pyrenomycetes. A few small tropical genera, Cora (Fr.), Rhipidonema 

 (Mattir.), Dictyonema (Mont.), and Laudatea (Johow.), are Basidiomyce- 

 tous, and two other tropical forms, Emericella (Berk.) and Trichocoma 

 (Jungh.), have recently been declared by ^lassee (Phil. Trans. Roy. Soc. 

 Lond., vol. 178, p. 305) to be Gasteromycetous 

 Lichens. The two last-named cases are by no g 



means satisfactorily established, and much more x 

 and better evidence must be forthcoming before 



Ar^" 



Fig. T.'i.o.—Coccocarpia violybdia Pers. Transverse section of 

 thallus. or. upper, and itr, under cortical layer. ;«, so-called 

 medulla ; g, algal cells ; r. rhizoids (x 6_o). (After Bornet.) 



they can be adopted as lichen-forming fungi. 

 Propagation is effected by the spores of the fun- 

 gal thallus, and an adaptation exists in certain 

 lichens examined by Stahl for the supply of algas 

 to the new lichen. Algal cells, the offspring of 



the thallus algae, which have been carried up into the hymenium, are cast 

 out along with the spores, so that, both falling in the same neighbourhood, 

 the germ-tubes of the spores find suitable hosts at once. This primary' 

 synthesis, however, probably takes place comparatively rarely in lichens as 

 a whole. Propagation is very abundant by means of soredes or brood -buds 



Fig. 281. — Ephebe pubcsccns 

 Fr. Branch of thallus with 

 two young lateral branches 

 (j-) ; g, algal cells ; h, hjphae 

 (x 500). (After Luerssen.) 



