100 GUIDE TO THE STUDY OF LICHENS. 



26. Cladonia leporina. Primary thallus rare. 

 Lobes narrow and much branched, quite rigid. 

 Podetia rather long, distinctly and uniformly twice 

 branched, quite smooth. Apothecia small. Disk 

 convex, scarlet. 



27. Cladonia amaurocroea. Primary thallus de- 

 ficient or wanting. Podetia long, slender, much 

 branched, terminal branches not bearing sperma- 

 gonia are pointed. Apothecia rather small. Disk 

 flat or slightly concave, margin and a central portion 

 often somewhat elevated, reddish-brown. Spores 

 lOya X 4.5/x. 



28. Cladonia rangiferina. Primary thallus often 

 wanting. Podetia long and rather slender, frequently 

 branching, smooth, greenish to ash-gray, terminal 

 branches short, somewhat recurved. Apothecia are 

 frequently wanting, small, simple. Disk convex, 

 brown. 



" Crabbe calls it truly, 



"'The wiry moss that whitens all the hill/ 



" ' Omnium lichenum copiosissima,' according to 

 Fries, — it is almost a cosmopolite, but its geo- 

 graphical range is, in various parts of the world, very 

 irregular and limited. In Northern Europe it is used, 

 like Certaria Islandica, as a nutrient and demulcent. 

 It is a social plant, covering in Lapland vast tracts of 

 country, and growing to a height of six to twelve 

 inches. The barren plains so covered are the favor- 

 ite and only pasture of the reindeer during winter; 

 the animals clear away the snow by means of their 



