LICHENE8. 



299 



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

 202, 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- 

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



Fig. 205. Germination of the spores of lichens, a, ripe aecogpore of 

 ospora affl, ais ; 6 and c, succesi-ive stages of germination, seen in optical section; 

 d, still later stage of germination, seen in perspective, e, beginning of germination 

 of ascospore of Ochrolechla pallescens ; f, the same at a much later stage, show- 

 ing the many young hyphse, much less magnified, ff, half of an ascospore of Per- 

 tutaria ceuthocarpaf seen in optical section, showing the pores in tho endospore 

 through which tbe hyphte pass out. The exospore is shaded in the figure, /x 

 190, the others X 390. After De Bary. 



<;ate the truth of the theory that they are the male sexual 

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

 organs of Helvellacea and Pyrenom.ycetes 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. 



