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? 



IV. 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- 



A B 



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

 cons per sa; a, spore cups. 



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

 spreading patches. Then* margins are much dented and 



