ORDER SACCHAROMYCETALES 



351 



Fig. 117. Saccharomycetales (?), Family Spermophthoraceae. Spermophthora 

 gossypii Ashby & Nowell. (A) Gametophytic, coenocytic mycelium. (B) Developing 

 gametangia. (C) Mature gametangia containing gametes. (D-G) Stages in union of 

 gametes. (H-J) Sporophytic mycelium bearing asci. (After Guilliermond : Rev. gin. 

 botan., 40:328-704.) 



less fusiform or lemon-shaped ascospore. As the eight ascospores enlarge 

 they use up the epiplasm. They usually remain in a rather compact 

 bundle even after the ascus wall disappears. Rarely a gamete germinates 

 parthenogenetically to form a septate mycelium bearing apparently 

 normal asci. Although the cytological details could not be made out 

 Guilliermond believed that the first two divisions of the ascus are meiotic 

 so that the fungus shows an alternation of a gametophyte with haploid 

 nuclei and a sporophyte with diploid nuclei. In 1936 he reported that in 

 cultures maintained for ten years the fungus had lost its power to produce 

 the ascogenous mycelium. The gametes from the gametangia no longer 

 underwent conjugation but germinated directly to repeat the gameto- 

 phytic generation. He suggested that Ashhya and Eremothecium may 

 represent a similar development in which sexuality has been lost and only 

 an asexual generation is present. (Fig. 117.) 



Guilliermond (1928) believed that Spermophthora occupies a position 

 intermediate between the Phycomycetes and Ascomycetes. Comparing 

 it with higher Ascomyceteae (e.g., Pyronema) he considered its sporo- 

 phytic stage with uninucleate cells and diploid nuclei to be homologous 

 to the system of ascogenous hyphae with cells containing pairs of haploid 

 nuclei. In Spermophthora the single diploid nucleus in the ascus divides to 

 form the nuclei of the ascospores ; in Pyronema the two haploid nuclei of 

 the ascus unite and then divide to form the nuclei of the ascospores. In 

 both the ascospores with their haploid nuclei give rise to a gametophyte. 

 In Spermophthora the gametangia produce individual gametes which are 

 set free and unite ; in the higher Ascomyceteae two gametangia (antherid 



