250 



THE FUNGI 



fertilized female cell, while the wall of the ascocarp is formed 

 from neighboring filaments (Fig. 219, Z>). The ascocarp thus 

 resembles in its development the sexually formed fructification 

 (cystocarp) of certain red algse such as Polysiphonia (Sec. 245). 

 The ascocarp, like the cystocarp, is a system of two tissues, one 

 derived from the fertilized female gamete (called an ascogonium] 

 and the other from the vegetative cells of the parent plant. 

 The phase in the life history beginning with the fertilized asco- 

 gonium and ending with the production of ascospores is an 

 asexual or sporophyte generation alternating with the sexual 



generation or gametophyte, as in the 

 red algse (Sec. 246). The waU of the 

 sac fruit is clearly a protective struc- 

 ture for the sacs, each of which gen- 

 erally develops six spores in the lilac 

 mildew, although eight nuclei are 

 present in the sac. 



The green and yellow mildews. 

 These are very common saprophytes 

 on bread, cheese, shoes, clothing, and- 

 other substances that mildew or 

 "mold" in dampness. They are 

 easily distinguished by their colors 

 and the structure of the conidial 

 fructifications. The green mildew is 

 Penicillium (Fig. 220, A), which is believed to give the peculiar 

 flavor to Roquefort cheese. The yellow mildew is Aspergillus 

 (Fig. 220, B). Their ascocarps are rather uncommon, especially 

 those of Penicillium. 



267. The cup fungi. Most of the conspicuous forms in this 

 very large assemblage belong to the order Pezizales. The sac 

 fruits are saucer-, cup-, or funnel-shaped (Fig. 221, A, B), fre- 

 quently colored yellow, orange, red, brown, or bluish, and in some 

 forms are three or more inches in diameter. The cup fungi are 

 almost all saprophytes, and are found on rotten logs and earth in 



FIG. 220. Green and yellow 



mildews 



A, the green mildew (Penicil- 

 lium) ; B, the yellow mildew 

 (Aspergillus) 



