. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . The latter is a tropicaland subtropical species with remarkable tooth-like apical connections, whichresult in very rigid filaments of cells. The apical attachment of this extra-ordinary species was first accurately described and figured by Johnson (94).In Cosmocladium the Cosmarium-\ike cells are held together by stalks ofmucilage, and the entire colony is quite small, branched in character, andfree-floating (fig. 226 A and B). In Oocardium,
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . The latter is a tropicaland subtropical species with remarkable tooth-like apical connections, whichresult in very rigid filaments of cells. The apical attachment of this extra-ordinary species was first accurately described and figured by Johnson (94).In Cosmocladium the Cosmarium-\ike cells are held together by stalks ofmucilage, and the entire colony is quite small, branched in character, andfree-floating (fig. 226 A and B). In Oocardium, the most curious of all thegenera of Desmids, the colony is hemispherical in shape, 1 to 2 mm. indiameter, and occurs attached to calcareous rocks in the beds of streams. Itconsists of a number of more or less parallel, radiating strands of mucus of. Fig. 220. Three species of Euastrum. A, E. aspenim Borge, x 468; B. E. serratum Joshua,x 468 ; C, E. inermius (Nordst.) Turn. var. burmense W. & G. S. West, x 468. a, front viewof cell; b, vertical or end view; c, side view. considerable thickness, each strand widening out towards the surface of thecolony and occasionally branching. In the free end of each mucous strand islodged a single cell, so arranged that its longitudinal axis is at right anglesto the axis of the mucous strand (fig. 226 D—F). The minute structure of the cell-wall was first studied by Klebs (85) whoexamined the nature of the mucilaginous outer coat and also demonstrated incertain species the presence of pores passing right through the wall. Haupt-fleisch (88) also contributed some information on this subject, more especiallywith regard to the extent and structure of the mucilaginous envelope. Someyears later Liitkemliller (94) described very minutely the pores in the cell-wall of Closterium, and eight years
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