. Fresh-water biology. Freshwater biology. THE FRESH-WATER ALGAE 145. 8i (82) Colony a plate of 4 or 16 spherical cells in a single layer, each with 2 cilia. Boundary of gelatinous envelop not distinct. Gonium Miiller. Cells oval, with two cilia and a pigment spot. Chroma- tophore single, parietal, hollow, with one pyrenoid. Re- production by successive divisions of each cell, forming a new colony; also, according to West, by isogametes. Gonium is one of the commonest of the Volvocaceae, occurring in almost all ponds and lakes. It is also one of the most beautiful of the group, as the colonies
. Fresh-water biology. Freshwater biology. THE FRESH-WATER ALGAE 145. 8i (82) Colony a plate of 4 or 16 spherical cells in a single layer, each with 2 cilia. Boundary of gelatinous envelop not distinct. Gonium Miiller. Cells oval, with two cilia and a pigment spot. Chroma- tophore single, parietal, hollow, with one pyrenoid. Re- production by successive divisions of each cell, forming a new colony; also, according to West, by isogametes. Gonium is one of the commonest of the Volvocaceae, occurring in almost all ponds and lakes. It is also one of the most beautiful of the group, as the colonies are ex- ceedingly regular and as they move they revolve, showing first the surface and then the edge. Fig. 147. Gonium pectorale Miiller. X 370. (After West.) 82 (81) Colony flattened, anterior portion rounded, posterior portion with three wart-like projections Platydorina Keloid. "The two faces compressed so that the cells of the two sides intercalate; flageUa upon both faces on alternate cells. Anterior and posterior poles of major axis are differentiated by the arrangement of the cells and by the structure of the envelope; long and short transverse axes differentiated by the flattening of the colony. Cells .similar, bi-flagellate, each with stigma, chromatophore, and pyrenoid. Asexual reproduction by repeated division of ^1 the cells, each forming a daughter ; Fig. 148. Platydorina caudata Kofoid. X 628. (After Kofoid.) 83 (80, 88) Colony spherical or spheroidal, but small. Cells not numerous. 84 84 (85, 86, 87) Colony of 4 or 8 elongated cells with irregular, pseudopodia-hke processes, arranged in a zone around the center of a firm gelatinous sphere . Stephanosphaera Cohn. Cells elongated, each with ciUa at the anterior pole which penetrate the gelatinous substance. Chromatophores irregular, with one or several pyrenoids. Each cell gives rise to a new colony by division; isogametes are also found. Fig. 149. Stephanosphaera pluvialis Cohn. X 425. (After Hie
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfreshwa, bookyear1918
