Sexuality in Synchytrium Brownii Karling

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Abstract
Planospores of S. brownii are sexually neutral in the beginning. Some of them gradually develop sexual tendencies and differentiate into two types of gametes, a receptive type which is the first to become sedentary and to absorb its flagellum, and a searching flagellate type which remains active for a longer time and retains its flagellum after becoming quiescent. Copulation occurs between gametes of these two types. As far as is known, neither alteration of sex of the gametes nor relative sexuality occurs. About 1–3 hours after pairing plasmogany occurs and within half an hour it is followed by karyogamy. The zygote is nonmotile, though it has a flagellum for a brief period. The oil globules also fuse in the zygotes. Occasionally the zygotes may have one or more supernumerary nuclei. Along with normal planospores, giant planospores are frequently produced which possess several normal flagella, nuclei and oil globules. They are considered to be monstrosities arising from unequal cleavage. The planospores that do not differentiate into gametes function as zoospores, infect the host, and develop into evanescent prosori. The flagella of the zoospores, gametes and zygotes are gradually absorbed and are not dropped off. Planospores emerging from sporangia of evanescent prosori or from germinated resting spores behave similarly. Also, differentiation of planospores into gametes is not hastened by over-ripening of the sporangia.

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