Growth Substances 



401 



Similar processes have been more fully studied in the water mold 

 Achlya by J. Raper (1939-1957), especially in A. bisexualis and A. ambi- 

 sexualis (Fig. 18-21). Experiments involving the transfer of mycelia 

 into water where plants of the opposite sex had been growing, and the 

 use of cellophane membranes, gave evidence that in the very regular 

 sequence of the sexual process four diffusible substances are concerned. 



A 1 Augments 

 'tf Inhibits — - 



Production of 



Antheridial Hyphae 



<r- 



— A Initiate 

 Mutually Aug. 

 — ^Initiates 



A- Complex 



AttractioW^^TVv 



Anth. HypriafF^ 



Delimitation \.\\ 

 of Antheridia ^ 



Production of 

 pi Initials 



Delimitation of 

 Oogonia 



ifferentiation of 

 heres 



> 



Maturation of 

 Oospores 



Fig. 18-21. Sex hormones in Achlya. Specific activities of substances A, B, C, and D 

 in the development and function of the sex organs. ( From J. Raper. ) 



