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result of diffusible hormones acting between compatible strains of 

 Neitrospora in the absence of hyphal contacts. Two compatible strains 

 inoculated in the opposite ends of a U-tube were alleged to produce 

 perithecia although no mycelial growth bridged the connecting tube 

 between them. Extensive efforts to duplicate these results were made 

 by Dodge (19) and Aronescu (2,3) who, by genetical methods, clearly 

 demonstrated that whenever perithecia appeared it was the result of 

 association of nuclei (hence of mycelia) of both compatible strains. 

 Further evidence for hormonal induction of perithecia by Moreau (39) 

 was unconvincing. 



The refutation of Moreau's extensive claims, however, by no means 

 indicates that hormones are not involved in the sexual process of 

 Neurospora and related forms. Two observations by Backus (9) would 

 indicate that they might well be. The first is that conidia placed on 

 medium or even on a glass surface over which the vegetative mycelium 

 of the compatible strain has grown will not germinate although they 

 retain their ability to fertihze compatible ascogonia. The second, lateral 

 branches arise from the trichogyne only at points normal to the shortest 

 distance to compatible conidia, microconidia, or hyphae, and that such 

 lateral branches grow directly to the fertilizing element. 



A case similar to the latter has been described by Zickler (72) in 

 Bombardia, in which the tips of the trichogynes are strongly attracted 

 by and grow to masses of microconidia, or spermatia. That this is a 

 chemotropic response was shown by i) a capillary filled with an extract 

 of spermatia and introduced into the agar in the vicinity of compatible 

 trichogynes caused directional growth of the trichogynes toward and 

 into the tip of the capillary, and 2) an agar block soaked in the filtrate 

 of liberated spermatia had the same directional effect on the growth of 

 trichogyne tips. Boiling had no adverse effect on the activity of the 

 extract and filtrate. 



It is only in a few species of the aquatic phycomycetous order 

 Saprolegniales, however, that sufficiently detailed information has been 

 obtained to approach a definition of the over-all hormonal coordinating 

 mechanism of sexual processes in the fungi. As early as 1881 de Bary 

 (10) suggested that a chemical substance secreted by the oogonial initial 

 induced the formation of antheridial hyphae and exerted over them a 

 chemotropic effect. Kauffman (24) induced antheridial production in a 

 species normally lacking the male sexual organs by adjusting the content 



