. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . hloroplast (sometimes twoin Conochsste) which in Ch&topeltis is often much lobed and perforated. Thereis usually a single pyrenoid, and Conoch&te comosa may store oil as a reserve(fig. 136 Do). Multiplication of the cells occurs by simple division which in Chsetosphse-ridium is transverse, the lower cell slipping out from under the upper oneand at once developing a sheathed bristle. 208 Tetrasporineae The genera are: Cheetopeltis Berthold, 18
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . hloroplast (sometimes twoin Conochsste) which in Ch&topeltis is often much lobed and perforated. Thereis usually a single pyrenoid, and Conoch&te comosa may store oil as a reserve(fig. 136 Do). Multiplication of the cells occurs by simple division which in Chsetosphse-ridium is transverse, the lower cell slipping out from under the upper oneand at once developing a sheathed bristle. 208 Tetrasporineae The genera are: Cheetopeltis Berthold, 1878 [inclus. M^/J-I>,-/>,-rtc Bohlin, 1894];Chsetosphseridium Klebahn, 1892 ; Dicoleon Klebahn, 1893 ; Conoch&te Klebahn, 1893 ;Diplochsete Collins, 1901 ; Polychxtophora W. & G. S. West, 1903 : OligochsetophoraG. S. West, 1911. Nordstedtia Borzi (1892) is a doubtful genus. Some of the above genera have been regarded by various authors as reduced forms ofthe Ulotrichales. Their habit as colonial unicells and their methods of multiplication donot, however, lend much support to the view that they have originated from filamentous. Fig. 136. A and B, Ch&tosph&ridium Pringsheimii Klebahn. C, Ch. Pringsheimii G. S. West. D, a form of Coiiochsete comosa Klebalin. ch, chloroplast; o, oil-globule. E—I, Oligochsstophora G. S. West; I, cell stained to show nucleus (»)and starch-grains (s). A—D, x 430 ; E—I, x 330. forms. On the other hand, the sheathed bristle such as occurs in Chgetosphasridium,Conocheete and Dicoleon is known elsewhere only in Coleochaste, the highest type of theUlotrichales ; and the curious unattached zoosporic forms of Coleochaste recently describedby Lambert (10 B), in which the thallus is reduced to a few irregularly grouped cells,might be said to throw light on the possible origin of the above-mentioned genera. Thereis, however, no evidence to show that the sheathed bristle is of any phylogenetic importance,and unsheathed
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