300 



GENERAL MORPHOLOGY OF PLANTS. 



Fig. 249. 



Much enlarged section of portion of 

 lining layer, showing the asci (i, 2, 3, 4) 

 with their contained spores. (After Sachs.) 



become separated from the main body. The fruiting stage, how- 

 ever, is that of the fungus. The fruit of the perfect stage in 



nearly all of the lichens is that of 

 the sac fungi with which they are 

 classed. There are a few tropical 

 forms with basidium fruit fungi. 

 A large number of the lichen sac 

 fungi have fruit bodies like those 

 of the black fungi, while in many 

 others they are like the cup fungi. 

 Other peculiarities of the lichens 

 can be noted after the study of a 

 few forms. 



448. The foliaceous lichens. 

 These are leaf-like, and grow 

 on rocks, fences, tree trunks, or 

 on the ground, where they are 

 more or less loosely attached. A 



common one on board and rail fences as well as on other woody 



structures is the star-shaped Physcia (Physcia stellaris). The 



plant is circular, rather 



closely appressed to the 



wood, and the margin is 



radiately divided into 



narrow irregular lobes, 



giving it a star-shaped 



form. It is dull gray in 



color. Scattered over 



the central portion are a 



number of cup-shaped 



or saucer-shaped bodies, 



the fruit bodies, or the 



apothecia, as they are 



called in the lichens. 



This fruit body is like that of the cup fungi. The sacs or asci 



are mingled with numerous sterile hyphae (paraphyses) which 



Fig. 250. 



Fruticose lichen (Cladonia cristatella), thallus 

 grayish green, the tips bright red. Grows on rotten 

 logs, etc. Natural size. 



