196 



CRYPTOGAMS 



menial surface is thrown into teeth; in the Pol}- 

 porus sub group (Fig. 328) the arrangement is 

 exactly the reverse, for the hymenium lines the 

 numerous pores. Branches, teeth, pores, and gills 

 are all devices for increasing the extent of spo- 

 riferous surface. 



326. Clavaria. 



327. Hydnum. 



328. Polyporus : p, pores of the 

 under surface. 



LICHENS (Figs. 329, 330) 



461. Lichens form gray or yellowish patches on rocks 

 and trees, festoons on the branches, and incrusting sheets 

 and spongy mats on barren soil. They are commonly 



known as " Moss " a wholly 

 wrong name, as will be seen when 



-a 



329. A lichen (Physcia stellaris) : 

 a, apothecia. 



330. Usnea barbata. 



