Imperfect Sexual Reactions in Homothallic and Heterothallic Mucors

Abstract

Imperfect sexual reactions were tested between homothallic species (including both homogamic and hetero-gamic forms) and ( + ) and ([long dash]) races of heterothallic species. Among the heterogamic hermaphrodites there are 2 sexual groups: (1) those with a ([long dash]) sexual tendency (Absidia spinosa, Dicranophora, Zygorhynchus moellen, Z. vuillemini,. Zygorhynchus sp.); these show strong reactions with ( + ) races and weak or no reactions with ([long dash]) races; and (2) those with a ( + ) tendency (Z. heterogamus). These show strong reactions with ([long dash]) races and weak or no reactions with ( + ) races. So far as investigated, all the races of a given species have the same sexual tendency. The terminal and lateral zygophoric hyphae of the hermaphrodites investigated are bisexual. The terminal hyphae take part more actively in imperfect sexual reactions than do the lateral branches. In the group of hermaphrodites with a ([long dash]) tendency, the large gametangium is shown to be (+) from its reactions with ([long dash]) races and the small gametangium is shown to be ([long dash]) from the reaction with (+) races. In the group with a (+) tendency, represented by Z. heterogamus, however, the large gametangium is shown to be ([long dash]) in reaction and the small gametangium to be ( + ). Representative hermaphrodites of these groups when grown together have given imperfect reactions. A small gametangium of the one group reacts with a small gametangium from the representative of the other group, or less frequently 2 large gametangia, one from each group, show a mutual reaction.