Sexuality in Physoderma pulposum Wallroth

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Abstract
In mixtures of planospores derived from 2 or more epibiotic sporangia of Physoderma pulposum several piano-spores function as gametes, pair, and fuse to form zygotes. Planospores from single epibiotic sporangia, or from germinating resting sporangia, however, do not copulate but infect the hosts (Chenopodium album and Atriplex patula) as zoospores and give rise to epibiotic sporangia. The gametes form pairs, clumps or long chains. After continuing together for more than 1 hour the pairs may separate, or ultimately settle down and fuse. In the latter case, 1 of the gametes of the pair becomes sluggish and settles down, whereas the other gamete remains active for some time more. When both are quiescent, they develop pseudopodia and fuse. The resulting zygotes are feebly motile, and they may be uni-or biflagellate, depending on whether or not the flagellum of 1 of the gametes was absorbed before plasnogamy. After a brief period of motility the zygote settles down and absorbs the flagellum. Karyogamy occurs as this state.