22 FRESH-WATER ALG^ OF THE UNITED STATES. 



The plant conjugates not like one of the Desmidiece, but 

 more like a Zygnemacece, in longer or shorter series ; often 

 when the zygospores are nearly matured, the cells of one 

 side separate and cause the other side to bend backward. 



Judging by these specimens the correctness of the generic 

 position of Bambusina may be questioned. 



Genus, SPHAEBOZOSMA. V. Des. U. 8. p. 28. 



S. PULCHRUM, Bail., var. CONSTRICTUM, Wolle. Plate LIX, 



fig. 12. 



Cells half as long as wide with a decided constriction in 

 each lobe between the axis and the apex. 



Diameter 70-75 yu. 



Lake near Kissimme, Florida. 



S. PULCHELLTJM ( Arch. ) Bab. Plate LIV, figs. 8, 9. 



Cells in outline oblong with the middle much inflated, 

 sharply incised and angles rounded ; ends narrower because 

 not at all or very slighted inflated ; apices square; varying 

 in length from one to nearly two diameters. 



Diameter 9-10 IJL. 



Pond waters, not rare. Syn. Spondylosium bambusioides, 

 Witt. S. pulchellum, Arch. 



S. MONILIFORME, Lund. Plate LIX, fig. 11. 



Series of cells often long, firm, somewhat twisted ; usually 

 included in a mucous envelope. Cells average one-half 

 longer than broad, deeply constricted, sinus obtuse out- 

 wardly enlarged, back more or less produced ;^seen from the 

 vertex triangular, sides somewhat retuse ; angles rounded, 

 isthmus sub -elongate, membrane smooth. 



Diameter about 20 /*. 



Not infrequent in quiet waters, Florida ; less frequent in 

 New Jersey, Minnesota and Pennsylvania. 



Genus, PENITJM. V. Des. II. S. p. 33. 



P. SPIROSTRIOLATUM, Barker. Plate LXI, fig. 17. 



Large, elongated ; single cells somewhat swollen in the 

 center, and tapering slightly towards the rotundo-truncate 

 ends ; the cell walls possessing a number of superficial, con- 

 spicuous, rather coarse striae, running in a spiral direction ; 

 these somewhat interrupted at a number of annular rib-like 

 projections varying in number ; these projections most 

 numerous towards the ends. 



