234 



ELEMENTS OP BOTANY. 



The mycelium of these is generally concealed in the substance 

 of the earth, decaying wood, or other material on which the 

 fungus grows, and the conspicuous portion of the plant is 

 that on which the spores are borne. 



Lichens, familiar objects encrusting rocks or hanging in 



Fig. 201. — Spore-Formation in Potato Blight (Pliytophthora infestans). 

 an unbranched stalk, proceeding from the mycelium 7ii in tlie interior of the 

 potato leaf, passing out of the epidermis e through the stoma up, and bearing 

 a single spore-ease ; B, an older group of stalks, showing spore-cases in various 

 (Both greatly magniiied, A more highly than B.) 



beard-like tufts from the bark of trees, which were once 

 regarded as constituting a separate division of the vegetable 

 kingdom, are now known to be curious examples of a kind of 



