THALLOPHYTES: FCNGl 



59 



a little sphere, which suggested the name Microsphmra 

 (Fig. 41). The heavy wall of the ascocarp bears beauti- 

 ful branching hair-like appendages (Fig. 43). 



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. 42). 

 The ascocarp, therefore, is 

 a spore case, just as is the 

 cystocarp of the Red Algse 

 (§ 33). The delicate sacs 

 within are the and, a word 

 meaning " sacs," and each 

 ascus is evidently a mother 

 cell within which asexual 

 spores are formed. These 

 spores are distinguished 

 from other asexual spores 

 by the name ascospore. 



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 pro- 

 duces 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) ro;; (V/ ('a, formed from a hyphal branch by abstric- 

 tion, by which the mycelium may spread rapidly ; and (3) 

 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. 



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

 simple illustration of Ascomycetes, but the group is a very 



'^-^^^ 



Fig. 42. Ascocarp of tlie lilac mildew, 

 sliowiiig branching appendages and 

 two asci protruding from the rup- 

 tured wall and containing ascospores. 

 — Caldwell. 



