84 SPECIES OF DESMIDS. 



f. Diameter i8/r, about 30 times as long as wide, smooth, ends 



rounded Brebissonii* 



f, " 20-2 1 ja; striated, ends rounded prelongum* 



f. " 36yw; about 20 times as long as wide, smooth, ends not 

 curved ensis* 



T Surface smooth; slightly tapering from the middle . strigosum, 42 

 ^T longitudinally striate only; diam. i i-i2//, juncidum, 38 



^[ " with 1-4 trans, striae; diam. 12-13/7, 



macilfntum, 38 



g. Ends inclined upward at a dorsal depression; ventrum slightly con- 



cave; striae fine, numerous '". . . turgidum, 41 



g. Ends suddenly contracted to a narrow point; cell slightly curved, 



attenitatum, 41 



g. Ends not suddenly contracted (//). 

 h. Cytioderm deeply striate; distinctly granulate or areolate, 



areolatum, 43 

 //. " more or less distinctly striate; cell linear-fusiform, 



15-24 times longer than wide acerosum, 41 



h. Cytioderm 9-12 longitudinally costate; cell fusiform, 4-5 times 



longer than wide subcostatum* 



h. Cytioderm more or less distinctly striate; cell semi-lunar, 5-6 times 



longer than wide Lunula, 40 



/. Diameter -^-^ to ^-g- in. (75-110^); cytioderm smooth, 



Ehrtnbergii) 45 

 /. Diameter 4^ to ^ T in. (40-60/1); globules a single row, 



moniliferum, 45 ; Leible i/iii\ 46 

 /. " . " " cell curved, rapidly tapering into 



narrow, somewhat upwardly-curved ends; cell 6-8 times 



longer than wide Ralfsii, 46 



/. Diameter T J^ to -g^-g- in. (35-45 //); 2 or 3 sutures in the middle; 



about 20 times longer than wide Delpontii* 



j. Cytioderm with many distinct striae; length 6-1 6 times the width; 



vacuole large striolatum, 42 



j. Cytioderm with fine striae; length 12-16 times the width; vacuole 



small decorum, 43 



j. Cytioderm with 5-8 distinct striae; length 6-8 times the width; 



vacuole large costatum, 42 



j. Cytioderm smooth; cell crescent-shaped, often subsemicircular (k). 

 j. cell not conspicuously crescent-shaped (/). 



k. Ends separated 7-10 times the diameter; width ygVir to T^OTT m - 



(16-20^) Diana, 44 



*F.-w. Algre, p. 23. 



