THALLOPHYTES: FUNGI 



275 



a little sphere, which suggested the name Microsplmra 

 (Fig. 241). The heavy wall of the ascocarp bears beauti- 

 ful branching hair-like appendages (Fig. 242). 



Bursting the wall of this spore fruit several very delicate, 

 bladder-like sacs are extruded, and through the transparent 

 wall of each sac there may 

 be seen several spores (Fig. 

 242). The ascocarp, there- 

 fore, is a spore case, just as 

 is the cystocarp of the Eed 

 Algaj (§ 174). The delicate 

 sacs within are the asci, a 

 word meaning " sacs," and 

 each ascus is evidently a 

 mother cell within which 

 asexual spores are formed. 

 These spores are distin- 

 guished from other asexual 

 spores by the name asco- 

 spore. 



It is these peculiar moth- 

 er cells, or asci, which give 



name to the group, and an Ascomycete, Ascus-fungus, or 

 Sac-fungus, is one which produces spores in asci ; and an 

 ascocarp is a spore case which contains asci. 



In the mildews, therefore, there are two kinds of asexual 

 spores : (1 ) conidia, formed from a hyphal branch by abstric- 

 tion, by which the mycelium may spread rapidly ; and (2) 

 ascospores, formed in a mother cell and protected by a heavy 

 case, so that they may bridge over unfavorable conditions, 

 and may germinate when liberated and form new mycelia. 

 The resting stage is not a zygote or an oospore, as in the 

 Algae and Phycomycetes, no sexual spore probably being 

 formed, but a heavy-walled ascocarp. 



185. Other forms. — The mildews have been selected as a 

 simple illustration of Ascomycetes, but the group is a very 



Fig. 242. Ascocarp of the lilac mildew, 

 showing branching appendages and 

 two asci protruding from the raptured 

 wall and containing ascospores. — S. 

 M. Coulter. 



