CLEAVAGE IN DIDYMIUM MELANOSPERMUM (PERS) MACBR.

Abstract

Many recent papers have confirmed the contention that cell division in the sporanges of algae and fungi is a process of progressive cleavage by surface furrows as against the older conception of simultaneous division by cell plate formation.Still the unique type of cell division by repulsion of the coarser cell inclusions and their heaping up in neutral planes which delimit the oospheres, described by Farmer and Williams (11) for the oogones of Fucus still remains unquestioned and little has been added to our knowledge of the mechanics of the cleavage process.'The older authors were for the most part dominated in their descriptions of spore formation in sporanges, first by the erroneous theory of cell formation put forth by Schleiden, and later by the conceptions of cell plate formation derived from studies on the higher plants.This older literature has been several times adequately summarized and need not be referred to further here (15, 29).Timberlake (31) describes the swarm spore formation in Hydro-