GENERA AND SPECIES. 93 



while others have several of these cup-like or dis- 

 coid expansions at regular intervals. The branching 

 forms also vary greatly as to size, manner of branch- 

 ing, etc. The color varies somewhat ; greenish-gray, 

 however, prevails. The podetia are hollow, and ex- 

 emplify a mechanical type especially adapted to re- 

 sist lateral forces (air currents). 



The apothecia are terminal upon the podetial 

 branches, or short apothecial stalks borne upon the 

 margin of the cup-shaped or cfiscoid expansions. 

 They are usually simple or more or less confluent, 

 globose, either brown or bright-scarlet. The scarlet 

 apothecia at once prove the specimen a species of 

 Cladonia. The spores are simple, elliptical, color- 

 less, and vary little in the different species. It must 

 also be remembered that some of the higher Cladonias 

 are constantly sterile. 



The Cladonias are widely distributed ; they occur 

 upon soil and rock, less commonly upon tree-trunks 

 and fences. They are northern in their range. 



1. Cladonia papillaria. Primary thallus crustose 

 to warty. Podetia (secondary thalli) short, smooth, 

 club-shaped, somewhat tapering near the apex. 

 Apothecia rare in some localities, small, more or less 

 confluent. Disk convex, brown. Spores simple, ellipti- 

 cal, colorless.* 



^ This species is quite common on soil in the hilly 

 districts of New Jersey and eastern Pennsylvania. 



» The spores of the Cladonias are so closely siiuilHr that the 

 measurements ami special descriptions will be oniiited in most 

 instances. The average measurements are 14 microns in length by 4 

 miorons in width. ' 



