Basidial Proliferation through Clamp-Formation in a New Sebacina

SUMMARYIn Sebacina prolifera conjugate nuclear division at the apex of a fertile hypha is accompanied by clamp-formation. The dikaryon reconstituted in the basidial stalk by this process moves out into the enlarged clamp and there undergoes conjugate division, with the formation of a second clamp. The binucleate apical cells thus formed develop into basidia, the second basidium being borne on the clamp at the base of the first. By repetition of the process a unilaterally cymose cluster of basidia is formed. Thus among the Basidiomycetes the clamp may function in the development upon a single cell of an indefinitely large group of gonotoconts exactly as does the crozier among the Ascomycetes. This phenomenon affords additional confirmatory evidence for the hypothesis of the homology of clamp and crozier and for the derivation of Basidiomycetes from Ascomycetes. A corollary of this hypothesis and this derivation is that the ancestral Basidiomycetes must have included clamp-bearing forms.The author desires here to record his indebtedness to the National Research Council for the fellowship during his tenure of which the present investigation was carried on; to Professor William H. Weston, Jr., and Dr. David H. Linder for suggestions and criticism during the course of the work and of the preparation of the manuscript; and especially to his wife, whose drawings illustrate the paper.