CRYPTOGAMS 



329 



4. Do you find fungi most abundant on young and healthy trees, or 

 on old, decrepit ones ? Account for the difference. (141,343,378.) 



5. Do you ever find them growing on perfectly sound wood anywhere ? 



6. Are they ever beneficial to a tree ? (86.) 



7. Is it wise to leave old, unhealthy trees and decaying trunks in a 

 timber lot? 



rV. LICHENS 



Material. — Specimens can be found almost everywhere, growing 

 on rocks, walls, logs, stumps, and trees. Some of the more common kind 

 are : Parmelia, recognizable by the shallow spore cups borne on the upper 

 surface of the thallus; Cladonia, by the little stalked receptacles, like 

 goblets, in which its spores are held ; Physcia, by its bright orange color. 

 Where practicable, it is well to have several different kinds for comparison. 

 Iceland moss {Cetraria islandica) can generally be obtained from the 

 grocers, and is a good example of an intermediate form between foliaceous 

 and fruticose lichens. 



If the specimens are very dry, they will be too brittle to handle conven- 

 iently, and should be moistened by soaking a short time in water. This 

 will render them quite flexible and also bring out the green color more 

 clearly. 



379. Examination of a typical specimen. — The com- 

 monest kind of lichens, and generally the most easily ob- 



FiG. 469. — Foliaceous lichens: A, Xanthoria (Physcia) parietina; B, Parmelia 

 conspersa; a, spore cups. 



tained, are those that grow on rocks and tree trimks in flat, 

 spreading patches. Their margins are much dented and 



