SPORULATION 327 



sterile mycelium of P. cactorum was washed in distilled water and trans- 

 ferred to the optimum concentration of the sexuality factor in 0.1 per 

 cent agar, oogonia began to appear within 15 hr., reaching the maximum 

 development in 3 days. This factor was also effective in inducing sexual 

 reproduction by P. erythroseptica, P. boehmeriae, and P. megasperma. In 

 addition, the presence of this sexuality factor induced the formation of 

 abundant oogonia within a week by 15 of the 20 species of Phythium 

 tested. However, it failed to induce sporulation of various Zygomycetes, 

 Ascomycetes, and Basidiomycetes. 



7-Carotene is associated with the male cells of the sexual phase and 

 not with the female cells of Allomyces (Emerson and Fox, 1940). This 

 specificity of association with the male cells indicates that 7-carotene may 

 be associated with sexual reproduction in some species of this genus. 

 No 7-carotene was found in the cells of these fungi in the asexual phase. 



Association with other organisms. That one fungus may influence the 

 sporulation of another has been known for a long time. Sporulation of 

 Alternaria and Helminthosporium was increased when they were grown 

 in association with certain other organisms (Porter, 1924). This paper 

 has a valuable bibliography on associative effects. 



The metabolic products of Aspergillus niger are known to promote 

 conjugation in three species of yeasts belonging to the genus Zygosac- 

 charomyces (Nickerson and Thimann, 1943). As a result of extensive 

 investigations, these authors found that part of the activity of Aspergillus 

 filtrate could be replaced by glutaric acid and riboflavin. While these 

 substances had some activity w^hen tested separately, the combination of 

 glutaric acid and riboflavin greatly exceeded the activity of either alone. 

 Riboflavin was shown definitely to be a component of the Aspergillus 

 filtrate. An autolysate from Zygosaccharomyces cells had a favorable 

 influence on sporulation by the same organism. From this experiment 

 and from the work of Lindegren and Hamilton (1944), who found that 

 ascus formation in yeast would take place only in portions of the yeast 

 colony where autolysis had taken place, it may be concluded that auto- 

 lytic products favor sporulation in some instances. Lindegren and 

 Lindegren (1944) found that addition of 2 per cent dried brewer's yeast 

 to a presporulation medium very favorably influenced the sporulation of 

 Saccharomyces cerevisiae. 



The presence of Bacillus weidmaniensis greatly stimulated growth and 

 production of macroconidia by Microsporum audouini (Benedek, 1943, 

 and Hazen, 1947). The addition of yeast extract to the medium had a 

 similar effect. A part of this stimulating effect was attributed to pyri- 

 doxine. The addition of yeast extract to a basal medium of honey agar 

 resulted in a marked increase in vegetative growth and macroconidium 

 production (Hazen, 1947). This stimulation was attributed to the pres- 



