GENERA AND SPECIES. 87 



77. CLADONIACE^. 



The representatives of this family are quite common 

 everywhere, occurring chiefly upon soil or rocky 

 ledges ; less commonly upon old fences, tree-trunks and 

 rotten wood. They are conspicuous as to size. The 

 thallus is peculiar in that it is made up of two parts: 

 one erect (secondary thallus or podetium, hence fruti- 

 cose), varies from simple to much branched ; the other 

 portion (primary thallus), spreading over the substra- 

 tum, varies from crustose {Bceomyces) to foliose {Cla- 

 donid). Strictly speaking, the upright portion of 

 Bceomyces is only a stipe, as in the preceding family. 



The apothecia are distinct and occur in all the 

 genera excepting ThamnoUa, which is always sterile. 

 They are more or less globose, disk convex to flat- 

 tened but never cup-shaped. No alg£e occur in any 

 part of the apothecia ; for that reason they belong to 

 the fungal type. (See Figs. 1 and 2, Plate IV.) 



KEY TO THE GENERA. 



Thallus (primary) crustose or warty. 

 Apothecia borne on unbranched thick stipes or nearly 



sessile 1. Bceomyces. 



Apothecia terminal on the erect tliallus (podetia). 



Erect thallus hollow, spores simple . . 2. Pilophoron. 

 Erect thallus solid, spores four-celled . 3. Stereonndon. 

 Thallus (primary) foliose or wantinfj, erect thallus hollow. 

 Apothecia usually present, disk brown or red, 



4- Cladonia. 

 Apothecia always wanting, erect thallus tapering, 



5. Thamnolia. 

 1. Bceomyces. 



The representatives of this genus usually occur 

 upon loamy or sandy soil in forest lands. Tlie primary 

 thallus is usually crustose ; in some of the Southern 



