52 SPECIES OF ALGvE. 



e. Cells, some at least, fusiform (/), 



e. Cells oblong or ovate, obtuse; 3-5 times as long as wide, 



obtusuS) 173 



/. Cells in a single even row; outer cells lunate . . dimorphus, 173 

 /. Cells usually all alike, acute, 3-6 times as long as wide, acutus, 173 



46. SCIADIUM. 

 a. Attached, umbellate; cells usually straight; base contracted into 



a short stem ............. arbuscula, 174 



a. Floating; a collection of umbels connected by a usually straight 



cell ................ gracilip(S) 175 



47. OPHIOCYTIUM. 



One or both ends spinous (a). 

 Without spines (c). 

 a. Both ends spinous (b). 



a. One end spinous, one end rounded; cells curved or coiled, 



cochleare, 175 



b. Cells arched or nearly straight, ends more or less enlarged, 



capitatum, 176 



b. Cells crescentic, CfosteriumAike, large .... cuspidatum, 176 



c. Cells small, curved, often in masses, ends rounded, parvulum, 176 

 c. Cells long, narrow, repeatedly coiled, ends rounded, circinatum, 176 



48. CHARACIUM. 



Sessile, no stipe; cells pyriform, apex somewhat produced, 



sessile, 177 



Not sessile, stipe present but often short (a). 

 a. Apex rounded or truncate (b). 



a. Apex acute (d). 



b. Stipe short, scarcely noticeable, end dilated; cells producing a 



short neck .............. acutum, 177 



b. Stipe longer, noticeable (c]. 



c. Apex produced as a thick neck; stipe brownish yellow, 



Pringsheimii, 177 

 c. Apex always rounded, cells obovate, stipe base not dilated, 



N&gelii, 178 



c. Apex rounded, truncate when open; stipe hyaline, 



heteromorphum, 178 



d. Producing a short neck; cells ovate ...... acutum, 177 



d. No distinct neck; lanceolate or sword-shaped, ends tapering, 



ambiguum, 177 



