LICHENE8. 



299 



threads (sterigmata), which line the inside of the wall (Fig. 

 203, D) ; upon the sterigmata are borne large numbers of 

 minute cells (the spermatia), which fall off and are per- 

 mitted to escape through the small opening at the apex of 

 the spermagonium. It is unknown whether these germinate 

 or not ; some botanists have supposed them to be sexual in 

 their nature — hence their name, spermatia ; the recent in- 

 Testigations of Stahl, to be referred to below, seem to indi- 



Fig. 305.— Germination of tlie spores of lichens, a, ripe ascospore of Megal- 

 ospora affiais ; &and c, 6ucces>ive stages of germination, seen in optical section; 

 d, still later staire of g:ermination, seen in perspective, e, beginning of germination 

 of ascospore of Ochrolechia pcUlesccns ; f, the same at a much later stfige, show- 

 ing the many younft; hyphffi. much less magnified, g, half of an ascospore of Per- 

 tusaria ceutkocarpa? seen in optical section, showing the pores in the endoppore 

 through which the hyphse p iss out. The exospore is shaded in the figure. / X 

 190, the others X 890.— After De Bary. 



cate the truth of the theory that they are the male sexual 

 elements ; on the other hand, their analogies to the similar 

 organs of Helvellacem and Pyrenomycetes point rather to 

 their conidial nature. 



Still other cavities (pycnidia) occur, in which spore-like 

 bodies are found, differing in size and other characters from 

 the spermatia. 



