24 DESMIDS OF THE TfXlTED STATES. 



Frequent in ponds of New Jersey, Pennsylvania, etc. 

 There are two forms very nearly allied, this H. undulata, and 

 Siihaerozosma excavatum (Ralfsi, both about the same thicli- 

 neas and same length of cell, and both in a colorless gelatin- 

 ous envelope ; the only point of separation is in the attach- 

 ment of the cells ; in the Hyalotheca the cells adhere by the 

 whole plane of the end, and in the Spaerozosma, they are 

 connected by two sessile glands on the margin. To my mind 

 this distinction is scarcely tenable. 



H. DUBiA, Kg. Plate I, fig. 14. 



Cells about as long as wide, not constricted, closely united 

 into short fragile filaments, without gelatinous sheath. 

 Diameter 13-21 yu. 



This form occurs now and then in waters of ponds in New 

 Jersey. As the name implies, it holds a somewhat dubious 

 position. It is without the mucous envelope characteristic of 

 the other species and is usually smaller. Fruiting specimens 

 have hot been observed. 



Reasoning from observations on the life history of an allied 

 genus, Bmnbusina, I venture to suggest that the forms re- 

 ferred to this species are merely undeveloped conditions of 

 other species. 



Genus, BAMBTJSINA, Kg. 

 Plate I, figs. 15-24. 

 Cells or joints barrel- shaped, surrounded by one or two narrow 

 median bands, closely united into articulate, nodose filaments. 

 Chlorophyl bodies and zygospores as in Hyalotheca. 



B. Beebissonii, Kg. {B. Borreri, Cleve ; Didynioprium Borreri, 

 Ralfs). Plate I, figs. 15-21. 

 Cells somewhat longer than broad, hub or barrel -shaped, 

 surrounded in the middle with two narrow bands, and another 

 often visible between these and the ends of the cells. 

 Diameter 18-25 yU. 



Frequent in quiet waters from Maine to Florida and far 

 west. A pond at Pleasant ilills. New Jersey, furnished me 

 with good conditions of development. The lowest traceable 

 stage is represented by fig. 17. A gelatinous sheath enclosing- 

 a series of green cells ; fig. 18, four cells around which the 

 envelope is diffusing ; these unite, end to enh, then widen 

 and produce a form as flg. 19 ; fig. 20 is somewhat more ad- 

 vanced, showing small notches 'in the sides ; fig. 21, the begin- 

 ning of the central inflation and the bands ; these continue 

 to develop until the perfect plant is produced. 



