THE LIFE HISTORIES OF THE FUNGI 273 



not be functional so that a condition of apogamy is present, as 

 in the water molds. 



The life histories of the sac fungi (Ascomycetes) are especially 

 interesting in relation to those of the red algse (Sec. 246). It is 

 known in regard to a number of types that the sac fruits (asco- 

 carps) develop as the result of a sexual process, corresponding in 

 this respect to the cystocarps. The ascospores are formed at the 

 end of the ascocarp phase of the life history just as the carpo- 

 spores are formed at the end of the cystocarp phase in the red 

 algse. Both ascocarps and cystocarps are, then, new genera- 

 tions developed between and alternating with the sexual plants. 

 They are sporophytes alternating with gametophytes. The for- 

 mula for the life history of a sac fungus with functional sexual 

 organs is then 



]> S (ascocarp) asex. s. (ascospore) 

 y 



S asex. s. G, etc., 



G and S standing for gametophyte and sporophyte, respectively, 

 and asex. s. for asexual spore. 



It must always be remembered, however, that the sac fungi 

 have a great variety of methods of asexual reproduction through 

 conidia, etc. Consequently sexual organs may be formed only 

 occasionally, as in the green mildew (Penicillium). There is 

 also probably much apogamy in the group, so that the sac fruits 

 are apogamously developed. 



The basidia fungi present the remains of an alternation of 

 generations in the rusts somewhat similar to that of the sac 

 fungi. The cluster cups are believed to be the beginning of a 

 phase that formerly followed a sexual process just as do the 

 ascocarps and cystocarps. However, the male organs (spermo- 

 gonia) of the rusts are no longer functional, and the cluster cups 

 must be considered as developing apogamousy, although there 

 is now a complicated history substituted for the original sexual 



