Sporangial Germination in the Genus Myzocytium

Abstract

While searching filaments of Spirogyra for members of the lower Phycomycetes, the thallus of a species of Myzocytium was found. The method of sporangial germination was later observed and proved to be at variance with those previously described for this genus, since no vesicle is formed at the tip of the exit tube. The zoospores mature within the sporangium and escape successively in single file. Thallus. In the young stages the thallus consists of an un? branched mycelial filament which is constricted at regular intervals to form a chain of ellipsoidal cells. At each constriction the nar? row channel is plugged with a spherical refractive granule giving the aspect of a thick septum. This is probably a cellulin granule corresponding with those described for the genera Gonapodya and Leptomitus. Similar refractive granules are scattered throughout the cytoplasm. The individual cells of a mature thallus are oval to ellipsoidal and measure 16-26 X 13-16/x. The number of cells in the chain varies from five to twelve. Asexual reproduction. The cells of a chain may all function as sporangia, or as sporangia and male and female gametangia. Each sporangium germinates by a single exit tube, about 3 /x in width, which is slightly constricted where it passes through the host cell wall. At about the time that the exit tube penetrates the wall, the densely granular content of the sporangium rounds up to form small globose bodies showing a slightly oscillating movement. At first this movement is more noticeable towards the center of the mass. In a few minutes it is present in the entire contents of the sporangium. The protoplasm in the exit tube then