. Fresh-water biology. Freshwater biology. 3i_(2p) An oval opening at the center between the transverse septa. Aptogonum Ralfs. ^ B Filaments often twisted, cells slightly longer than broad, with three or four projections on each end which exactly meet others on the adjoining cells, some- times slightly constricted. Several py- renoids in each cell, from which radiate the plate-like chromatophores. The genus Aptogonum is included by many under Desmidium, but the space at the center between two adjoining cells, the lack of the narrow central construc- tion, and the greater length of the cells w
. Fresh-water biology. Freshwater biology. 3i_(2p) An oval opening at the center between the transverse septa. Aptogonum Ralfs. ^ B Filaments often twisted, cells slightly longer than broad, with three or four projections on each end which exactly meet others on the adjoining cells, some- times slightly constricted. Several py- renoids in each cell, from which radiate the plate-like chromatophores. The genus Aptogonum is included by many under Desmidium, but the space at the center between two adjoining cells, the lack of the narrow central construc- tion, and the greater length of the cells would seem to distinguish it from Des- midium. Fig. 116. Aphgonum baileyi Ralfs. a. side view. b. end view. c. optical section. X 425. C (Original.) 22 (4) Cells not united into filaments 23 23 (33) Cells not constricted at the center, or at the most only very slightly so 24 24 (25) Cells crescent-shaped; tapering toward both ends. Closterium Nitzsch. Cells varying from short, thick cells swollen in the middle to very slender cells sometimes bent in the shape of an S. Membrane smooth, or longitudinally striated, rarely with a yellow hue. Chromatophores in each cell-half of several radially-placed plates, including one or more rows of pyrenoids; at each end a large vacuole containing moving granules. Fig. 117. Closterium moniiiferum var. concavum Ehrenberg. X about 200. (Original.). 25 (24) Cells cylindrical or fusiform 26 26 (27, 28) Chromatophore one or more parietal, spiral bands. Spirotaenia Cells straight, oblong, cylindrical, or fusiform, with rounded ends. Chroma- tophores one or several parietal bands with pyrenoids. Fig. 118. Spirotaenia minuta Thuret. X 365. (After West.) 27 (26, 28) Chromatophore star-shaped, one in each cell-half. Cylindrocystis de Bary. Cells with rounded ends, often oval in outline. Chroma- tophores two, star-shaped, many rayed, each enclosing a pyrenoid at the center. Fig. 119. Cylindrocystis diplospora LundeU. X 375. (Original.) 28 (26
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfreshwa, bookyear1918
