I08 SPECIES OF DESMIDS. 



rr. Cells spinulose, a short, irregular process on each side, 



controversum, 143 

 rr. Cells spinulose on the margins of the long, colorless, diverging 



arms aspinosum, 143 



ss End view triangular or 3-radiate (////). 

 ss. 4 or 5-angular or radiate (//). 



ss. End view circular, with usually 9 short, marginal, notched pro- 

 cesses Eloiseanum, 149 



//. End view margins smooth; spines short; semi-cells in front view 



twice as wide as long avicula, 123 



//. End view margins smooth; spines short; semi-cells in front view 3. 



'or 4 times as wide as long commutatum, 124 



//. End view margins smooth; spines on the angles only, very long, 



longispinum, 145. 

 //. " spines on the margins and surface as well as on 



the angles MiimesoUnsc.** 



tt. End view margins verrucose, the verrucae emarginate or not, 



forficulatum , 144 



//. " denate, angles usually 3 . monticulosum, 144 



uu. End view margins smooth, concave; angles notched, 



quadr angular e, 1 45, 

 uu. " crenate; spines long, divergent, 



Novce. Ccesarece, 145, 

 uu. u spinous; angles produced, furcate, 



forficulatnm, 144 



w. End view triangular; aculei short, Hystrix, 142; tridentifertim, 142 

 vv. " " spines long, colorless, 



tricornututn, 145; triquetrum** 

 vv. End view 4-angled, angles broadly rounded, spines scattered; 



sides concave Hystrix, 142 



w. End view 5 -angled, sides concave Brasiliense^ 146 



wu>. Angles with numerous setae as long as the lobes; cells in front 



view cruciform cruciat-um, 142 



unt'. Angles with 4 teeth, 2 projecting upward, 2 downward, 



cerberus, 142 

 wu>. -2 spines; margins concave, spinous 



quaternium, 144 



xx. Sides unequally produced, spinulose or spinous, controversum, 143 

 xx. Sides equally produced, spineless; angles spinous aculeatum, 140 



**F.-w Algae, p. 41 et seq. 



