. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . denticulatus the poles ofall the cells are furnished with minute teeth; in S. granulatus the walls aregranulated; and in S. costatus and S. acutiformis the cells are longitudinallyridged. It has been shown by Petersen (11) that the cells of some speciesof this genus are furnished with very delicate bristles (fig. 130 F). Chodat * 1 Wille associates this Alga with Coccomyxa, but there is little doubt that it is most closelyallied to Ankistrode
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . denticulatus the poles ofall the cells are furnished with minute teeth; in S. granulatus the walls aregranulated; and in S. costatus and S. acutiformis the cells are longitudinallyridged. It has been shown by Petersen (11) that the cells of some speciesof this genus are furnished with very delicate bristles (fig. 130 F). Chodat * 1 Wille associates this Alga with Coccomyxa, but there is little doubt that it is most closelyallied to Ankistrodesmus, especially to those forms which are normally enveloped in mucus; andalthough the actual division-plane of the cell is transverse, the daughter-cells as often as notgrow by sliding obliquely past each other. Elakatotlirix gelatinosa occurs in the lakes of Norwayand the English Lake District (Wastwater). Selenastreae 203 & Malinesco (93) and also Grintzesco (02) have done considerable experi-mental work on Scenedesmus obliquus (= S. acutus), and have confirmed theobservations of others that this Alga has a Dactylococcus-sfate (fig. 128 B). Fig. 130. A and B, Actinastrum Hantzschii Lagerh. x 400 (after Lagerheim); B shows thedivision of the mother-cells. C—E, Desmatractum plicatttm W. & G. S. West, x , Scenedesmus obliqwis (Turp.) Kiitz. var. ditnorphus (Turp.) llabenh., showing the bristlesat the extremities of the cells, x 730 (after Petersen). which is identical with Dactylococcus infusionum Nag. Grintzesco alsoshowed that remarkable malformations are produced by the culture ofScenedesmus obliquus on a nutritive medium of agar and glucose, and thatthis species can liquefy gelatin. He attributes the extensive geographicaldistribution of this plant to the ease with which it adapts itself to differentmedia and different temperatures. The members of the Selenastrese usually occur in the smaller ponds and pools, wherethey are often found in great quantity; some of
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