. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . ts appearance onthe new semicells as they assume the normal size. As a rule the two newsemicells, and therefore the daughter-cells resulting from division, remainattached until they are full-grown. Chloroplasts appear in the new semicellsat a comparatively early age, but at present there is no exact informationconcerning their origin. The pyrenoids in many cases certainly arise denovo. In the unconstricted genus Closterium2, the only genus of
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . ts appearance onthe new semicells as they assume the normal size. As a rule the two newsemicells, and therefore the daughter-cells resulting from division, remainattached until they are full-grown. Chloroplasts appear in the new semicellsat a comparatively early age, but at present there is no exact informationconcerning their origin. The pyrenoids in many cases certainly arise denovo. In the unconstricted genus Closterium2, the only genus of Desmids inwhich cell-division has been minutely studied, the process of division, althoughsimilar in essential points, differs in details from that which occurs in con-stricted Desmids. Lutman (11) has shown that in Closterium Ehrenbergiiand Cl. moniliferum the first visible appearance of division in any individual 1 The details of the early stages of cell-division yet require careful investigation. 2 There are several slightly constricted species of this genus; notably Closterium BrauniiReinsch (67) and Cl. subcompactum W. & G. S. West (02).. 368 Conjugate cell is the pinching in of the two chloroplasts at a point about a third thedistance from the middle to the extremity, and that the division of thechloroplasts is entirely distinct from that of the cell. This constriction occursaltogether inside the plasmatic membrane of the cell and is probably the
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