Fresh-water Alga. 77 



lamellosa, lamellae exteras (et vetustse) plus minusve irregulariter 

 dissociata?. Propagatio autosporis 2 vel -i e divisione transverse vel 

 oblique in cellula matricali ortis. 



94. Ecdysichlamys obliqua, sp. unica. 



Character idem ac generis ; cellulis parvis, diametro circiter li- 

 1^-plo longioribus. 



Long. cell. 8-7-13-7 ft ; lat. 5-8-8 fi. (Figs. 18-29). 



Angola. Forming a thin green stratum, one layer of cells in 

 thickness, with Pleicrococcus disscctus, on sand-grains in a shallow 

 depression which received the water from the bath-rooms of the 

 cable-station, Mossamedes. 



This genus undoubtedly stands near to Oocystis, Nag., but differs 

 in several important respects. In the first place the cells of this alga 

 form a dark green, compact, attached stratum, one layer of cells in 

 thickness, whereas all species of the genus Oocystis are free-floating, 

 solitary or gregarious colonies. The oblique nature of the cells, 

 with one side very much flattened, is also characteristic, although 

 one known species of Oocystis possesses asymmetrical cells (vide 

 0. asymmctrica, W. & G. S. West, in Journ. Eoy. Micr. Soc, 

 1894, p. 14, t. 2, f. 27). 



The outer layers of the cell-wall, which in all the cells is very 

 firm as in Oocystis, are often thrown off in a manner comparable 

 with the exuviation of the outer layers of the wall which occurs in 

 Nephrocytium ecdysiscepanum, W. & G. S. West. The outermost 

 layer often alone separates and exists as an outstanding envelope 

 such as may be seen in Oocystis parva, W. & G. S. West {vide 

 G. S. West in Journ. Bot., 1899, t. 394, f. 14-16). 



The chloroplast is very massive and practically fills the whole 

 cell. It contains one, or very rarely two, conspicuous pyrenoids, 

 such as do not occur in any species of Oocystis except 0. natans, 

 (Lemm.) Wille. 



In the formation of the autospores the division of the protoplast 

 is somewhat variable. When only two autospores arise in the 

 mother-cell, the division is often exactly transverse, whereas at 

 other times it is oblique. When four autospores are being formed 

 in the one mother-cell, two oblique division-planes are formed 

 simultaneously. 



Each pole of the cell is terminated by a very delicate and scarcely 

 discernible apiculus. 



95. Tetraedron minimum, (A. Br.) Hansg. 



Karoo. In sulphureous spring at Pappekuil ; 2.12.08. 

 Little Namaqualand. In dam at Pella ; 8.1.09. 



