. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . commonest Green Alga in the world must in future beknown as Protococcus viridis Ag., but it also determines the family Protococcaceas, which cannot 192 Tetrasporineas incrustation in the temperate climates of the northern and southern hemi-spheres, generally on the windward side of tree-trunks, palings, stones, walls,etc. The cell-walls are strong and of some thickness, and the Alga is ableto withstand considerable desiccation. The products o
. Algæ. Vol. I. Myxophyceæ, Peridinieæ, Bacillarieæ, Chlorophyceæ, together with a brief summary of the occurrence and distribution of freshwat4er Algæ . commonest Green Alga in the world must in future beknown as Protococcus viridis Ag., but it also determines the family Protococcaceas, which cannot 192 Tetrasporineas incrustation in the temperate climates of the northern and southern hemi-spheres, generally on the windward side of tree-trunks, palings, stones, walls,etc. The cell-walls are strong and of some thickness, and the Alga is ableto withstand considerable desiccation. The products of cell-division do notseparate readily, so that compact groups of 2, 4, or 8 cells are frequent,(fig. 118 J.). The cells contain a single much-lobed parietal chloroplast, whichappears sometimes as several parietal cushions and at other times is somassive as to fill almost the whole cell. Normally the chloroplast is withouta pyrenoid, but a pyrenoid has often been described and figured as occurringin certain of the cells (see fig. 118 A, py), although it yet remains to bedecided how far these records are correct1. Under certain conditions, usually. Fig. 118. A, ProtococcuA riridis Ag. ( = Pleurococcus vulgar is Menegh. of most modernauthors). B, P. rufescens Kiitz. var. sanyuineus (W. & G. S. West)—. All x , chloroplast; p, protoderma-state ; pa, palmella-state ; pg, red pigment (hoematochrome?)dissolved in globule of oil ; py, pyrenoid. of excessive moisture, short filaments of cells, are formed which exhibit asimple type of branching. This form, which is almost entirely a culture-state and was described by Snow (99) as Pseudopleurococcus, greatlyresembles the genus Protoderma and is known as the palmella-state may also be developed in cultures. Reproduction occursby the formation of one or many aplanospores. Zoogonidia and isogametes in future be used in the sense of Oltmanns (04), West (04), Chodat (09) or Wille (09). Thismay seem undesirable
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