. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . renoid. In Eremosphxra there are numerous parietal chloroplasts, andin most species of Oocystis there are several (vide fig. , C, D and E).The protoplast contains a single nucleus located in the central part ofthe cell. Multiplication sometimes occurs by the division of the mother-cell along 13—2 196 Tetrasporineae transverse (Elakatothrix) or oblique (Arikistrodesmus falcatus var. acicularis,fig. 129 C) planes into two or four daughter-
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . renoid. In Eremosphxra there are numerous parietal chloroplasts, andin most species of Oocystis there are several (vide fig. , C, D and E).The protoplast contains a single nucleus located in the central part ofthe cell. Multiplication sometimes occurs by the division of the mother-cell along 13—2 196 Tetrasporineae transverse (Elakatothrix) or oblique (Arikistrodesmus falcatus var. acicularis,fig. 129 C) planes into two or four daughter-cells. Reproduction takes placeby the successive divisions of the protoplast to form 2, 4 or 8 spore-likebodies, which in most cases assume the characters of the mother-cell beforebeing liberated. These are autospores. In the coenobic forms each mother-cell gives origin to a new colony—an autocolony (figs. 128 C, and 133 C and D).The wall of the mother-cell is either ruptured or becomes converted intomucilage, and in Oocystis may become greatly distended to form a wideenvelope enclosing the zoogonidia nor gametes H Fig. 122. A—F, Oocystis submarina Lagerh. A, vegetative cell; B, young colony; D and E,Tetraedron-like cells formed within old mother-cell-wall of Oocystis; C and F, developmentof Tetraedron-like cell to form two (C) or four (F) Oocystis cells. A and B, x 995 ; D andE, x570; C and F, x 610 (after Wille). G and H, Scotiella antarctica Fritsch. G, singlecell viewed with the principal ridges parallel to the substratum, x 830 ; H, optical section,x 430 (after Fritsch). I and J, Scotiella polyptera Fritsch. /, side view; J, oblique endview to show course of ridge?, x 1100 (after Fritsch). A and L, two side views of Scotiellanivalis (Chod.) Fritsch, x about 800 (after Chodat). The Alga? of this family are little removed from the most primitive formsof the Chlorophyceae, and it is probable that the characteristic autospores aremer
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