Sexual Hormones in Achlya: V. Hormone A', a Male-Secreted Augmenter or Activator of Hormone A.

The r6le of specific sexual hormones in the sexual reaction of two hetero-thallic species of Achlya has been described in earlier papers of this series.' Four specific substances were postulated, two secreted by the 9, bringing about specific reactions in the e, and two secreted by the c, inducing specific responses in the 9. On the basis of evidence available at that time it seemed that the entire sexual reaction was initiated wth the secretion of hormone A by the vegetative mycelium of the 9, which induced the formation of sexual organ initials, antheridial branches, on the ed. In the course of a more detailed analysis of the response of the ci plant to hormone A from the 9 ,2 it was found that the vegetative mycelium of the a" secreted some factor which profoundly influenced its response to hormone A from the 9. This factor, produced by the vegetative a plant independently of any response to the 9, will hereafter be referred to as hormone A' (A prime). The species and sexual strains used in this work are those previously employed in the work on sexual hormones in Achlya: Achlya bisexualis 9 for the production of hormone A," and Achlya ambisexualis ci as test plants for the assay of hormone A and for the detection of hormone A'. The method of testing is that previously described2 and the standard hormone A solution is the same as that used throughout the work on the characterization of this hormone.4 Any modifications of previously described methods or techniques will be described in the body of the paper. The discovery of hormone A' came about quite by accident. In the analysis of the response of the c plant to hormone A, a series of experiments was performed in an attempt to determine whether the hormone was used up, i.e., removed from the test solution during the course of the reaction , or whether it produced its effect through the catalytic activation of some existing physiological system, the hormone thus remaining un