SPECIES OF DESMIDS. 85 



k. Ends separated 7-10 times the diameter; width -g-J^ to yoVir m - 



(25-28/1) dcuminatum, 44 



k. Cell 6 to 8 times longer than wide, ends obtuse; width T1 ig T in. 



(14^) ... .... Jenneri, 44 



k. Cell 6 to 8 times longer than wide, ends obtuse; width 2o T 00 in. 



(i2//) parvulum, 45 



k. Cell 8 to 12 times longer than wide, nearly semicircular, ends v 



sharp; width 2^ to 3 T Vo in. (8-ioyw) ..'.",. Venus, 44 

 /. Cell stout, ends broadly rounded; width -^ to y^o in. (25-30/1), 



cucumis, 40 

 w. Beaks slender, nearly as long as the body, ends obtuse, curved, 



Kuetzingii, 47 

 #2. Beaks thin, y^ as long as the fusiform body . . rostratum, 46 



14. DOCIDIUM. FIG. 14. 



Suture a projecting or conspicuous rim (a). 



Suture not projecting (d). 



a. Cytioderm hirsute; semi-cell with 3 or 4 undulations, spinosnm, 51 



a. Cytioderm not hirsute (b). 



b. End dentate or crenate; semi-cell with i basal inflation (c). 



b. " " " semi-cell with 4 regular inflations; teeth 



on the margin constrictum, 50 



b t End dentate or crenate; semi-cell with 3 or more inflations; teeth 



below th; margin nodulosum* 



b. End truncate or rounded; semi-cell with i or 2 basal inflations, 



Trabecula, 48; truncatum, 48 



b. k4 semi-cell undulate to the contracted end, 



crenulatum, 47 



b. kk " 1-2 undulate at base only, 



Archerti* 



c. End with i tooth on each angle Flowtowii, 49 



c. End crenulate with tubercles coronatum, 49 



d. Cytioderm hirsute; base of semi-cell slightly inflated, hirsutum, 51 



d. Cytioderm not hirsute (<?). 



e. End dentate or crenate (/). 



e. End not dentate nor crenate (/). 



f. Semi-cell with 4 or more inflations (//). 



f. with whorls of quadrangular prominences, 



verrucosum, 52 



f. " with 20 or more constrictions costatum, 5 3 



/. " with i inflation (g). 



*F.-w. Algae, p. 25. 



