EUASTBUM. 107 



comparison, scores of sketches made of plants from as many 

 localities in different States from Vermont to Florida and 

 westward to Minnesota, this division suggested itself as the 

 most feasible and natural. I retain the old names but with 

 somewhat modified diagnosis. 



E. binale, (Turpin). Ralfs. Plate XXVII, figs. 23, 24. 



( Vlls minute, about one-half longer than broad, oblong-oval ; 

 semicells with their basal portions entire ; slightly contracted 

 beneath the end- ; apex dilated, it- central notch acute, broad, 

 gaping. Transverse view with two lateral inflations; ends 

 truncate, angles rounded. 



I >iameter I 5-25 //. 



Plant.- of this species have features in common with /-.'. 

 simplex, bul may be readily recognized by the proportion- 

 ately shorter form and the pouting separation of the end. 



E. compa< if \i, Wolle. Plate XXVII. figs. 28, 29. 



Y ery small, suborbicular, little longer than broad ; semicell 

 broad, transversely oval ; apex a slight protuberance with a 

 linear incision ; two small prominences, one on each sideof the 

 apical projection. 



Diameter 20-22 ".; length 28 ". 

 P I, Pennsylvania. 



E. OBTUSUM, Wolle. Plate XXX' 1 1, fig. 31. 



Minute, twice as longaswide; semicell obovate, base flat- 

 tened, sides somewhat diverging, end broadly rounded with 

 linear incision in the centre. 



Diameter 14 '/. ; length 25 u. 

 Pond.-. Pennsylvania, 



E. abbuptum, Nord. Plate Lll. figs. 21, 22. 



Cells one and one-halt' times as long as broad ; constriction 

 deep, narrow linear : semicells trilobed, lateral lobes somewhat 



protruding above the base, near the middle; ends truncately 

 rounded and usually dentate or granulate ; end lobe incised bifid, 

 with exterior angles furnished with short spines ; transverse 

 view rectangular with large central inflation, end margin more 

 or less undulate granulate, or sometimes retuse. 



Diameter 28-30 ;>.. ; length 40 //. 



