CLOSTERIUM. 39 



C. oracilb, Breb. Plate VI, figs. 4, 5. 



Long cylindrical, 2030 rime- as l<>im as broad, Dearly 

 straight, ends somewhat curved and slightly reduced in thick- 

 ness; cytioderm smooth and colorless. Zygospores according 

 to Brebisson quadrangular, with rounded angles each of which 

 bears a >li<>rt spine. 



Diameter 56 ,".: zygospore 28 30 u. long ; 22 _". broad. 



Not infrequently intermingled with other desraids from 

 ponds, New Jersey, Pennsylvania, etc 



( . lanceolati m, Kg. < '. tenue, Bailey). Plate VIII, fig. 1 I. 

 Cells semi-lanceolate, 6 10 times longer than broad, grad- 

 ually tapering, ends subacute, chlorophyl fillets several ; larger 

 granules in a single series. Empty frond colorless and desti- 

 tute "t' striae. 



I Hameter 5< -55 u. 



Pools, Florida ; Ne* York, Bailej . 



Stouter and proportionately shorter than < . acerotmm. 



C. DlDYMOTOCi M, Corda. I Man V I I I . figs. I 2, I -"I. 



Broad cylindrical, slighth curved, 6 12 times louger than 

 broad, slighth tapering towards the ends which are broadly 

 truncate, square ; vacuole distincl containing main "dancing 

 granules;" cytioderm yellowish, finely longitudinally striate. 



Diameter 30-32 u. 



N t abundant, bul turn- up now and then with other forms, 

 in smaller pond- of Pennsylvania and V \\ Jersey. 



( '. de< i bsatum, Kg. Plate V I. figs. 9, 10. 



Cylindrical, curvature scarcely appreciable; 712 times 

 longer than broad; verv slightlv tapering near the obtuselv 

 rounded end-, cytioderm distinctly decussately striate. 

 Diameter 20-25-30 ". 



Frequent in ponds, Mt. Everett, Massachusetts, Augusl 

 1882, and ponds northern part of New Jersey. Kutzing of 

 Germany appears to have been the only individual who 

 observed this species. He sent a drawing to Ralfs, but he 

 questioned the correctness of his friend's vision ; he remarks, 

 " Prof. Kutzing represents the r-triae as regularly crossing each 

 other, mi as to form diamond haped reticulations. As this 

 appearance \$ poj unusual in dried specimens, when the 



