. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . The time elapsing beforethe fusion of the nuclei is apparently variable, being much shorter in somespecies than in others. According to Kurssanow (11) the male chloroplastsdisintegrate immediately after the formation of the zygote-walls. The nucleus(fusion nucleus) of the zygote thereupon divides twice, three of the nucleidegenerating and one assuming the characters of the true states that there is no conjugation of t
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . The time elapsing beforethe fusion of the nuclei is apparently variable, being much shorter in somespecies than in others. According to Kurssanow (11) the male chloroplastsdisintegrate immediately after the formation of the zygote-walls. The nucleus(fusion nucleus) of the zygote thereupon divides twice, three of the nucleidegenerating and one assuming the characters of the true states that there is no conjugation of two of the secondary nuclei( two of the four produced by division of the fusion-nucleus of the zygote)such as Chmielewski describes in Spirogyra. It must be confessed, however, Zygnemeae 345 that the published statements regarding the cytology of conjugation inZi/c/nema are not at all in agreement with one another, and that much furtherinvestigation is still required. It is necessary to consider the case of Zygnema ericetorum (Kiitz.) Hansg. Alga has a world-wide distribution and in temperate countries it lives equally well in. Fig. 215. Zygnema ericetorum (Kiitz.) Hausg. A and B, fully conjugated specimens; C, anearly stage in conjugation ; I) and E, stained specimens to show the chloroplast and , chloroplast; cj, conjugation-canal; g, gametangium; «, nucleus; py, pyreuoid; z,zygospore. A—C, x425; D and E, x 1500. Note. A—C were originally described under the name of Zygnema pachydermum W. &G. S. West. water or on damp heaths or peaty moors, not infrequently assuming a purple or violetcolour owing to the appearance of phycoporphyrin in the cell-sap. In 1858 De Baryattempted to put the genus Zygogonium upon a new footing, including in it Z. ericetorum 34(5 Conjugate and Z. didymum1, the generic character being the formation of progametaHgia whichultimately fuse to form the zygospore. He illustrated this by two figures of conjugatingfilame
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