. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . substance appears toreside wholly in the nucleolus. Reproduction is purely asexual and may occur in a variety of ways,depending largely upon the conditions of environment, any change ofconditions usually resulting in a corresponding variation of the reproductiveprocess. Rostafinski & Woronin (77) worked out the different methodsof asexual reproduction and the final result in every case is the productioneither of zoogonidia or of cysts (someti
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . substance appears toreside wholly in the nucleolus. Reproduction is purely asexual and may occur in a variety of ways,depending largely upon the conditions of environment, any change ofconditions usually resulting in a corresponding variation of the reproductiveprocess. Rostafinski & Woronin (77) worked out the different methodsof asexual reproduction and the final result in every case is the productioneither of zoogonidia or of cysts (sometimes termed aplanospores), thelatter often becoming hypnocysts. The whole vesicular plant becomes a huge Botrydiacese 415 zoogonidangium when submerged in water and the zoogonidia escape ingreat numbers from an apical opening (fig. 265 2). The zoogonidia are smalland ovoid in shape, with two chromatophores and two unequal cilia. Ifthe plants are wet, but not submerged, the zoogonidia do not swarm out,but round themselves off as non-motile gonidia, each of which can grow intoa new plant. If, on the other hand, the plants become dry, such as when. Fig. 265. 1—4, Botrydium granulatum (L.) Grev. 1, vegetative plant; 2, the escape of zoogonidia;3, the formation of cysts in the rhizoids; 4, four zoogonidia. 5, Botrydium WallrothiiKiitz. 1—3 and 5, x about 50; 4, x about 800. (After Kostafinski & Woronin, from Oltmanns.) The zoogonidia are here depicted with only one ciliurn, but it has been definitelyshown that they possess two of unequal length. exposed to strong sunshine, the cytoplasm with the nuclei and chromatophorespasses down into the rhizoids and there becomes divided up into a number ofseparate portions which surround themselves with new walls and become cysts (fig. 265 3). The cysts may develop in more than one way. Ifsubmerged in water they form zoogonidia at once; if placed on damp earthin the light each cyst puts out a rhizoid and develops directly into a n
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