110 DESMIDS OF THE UNITED STATES. 



Minnesota. A number of varieties of this species have 

 been described by specialists in different countries. The 

 present is not Ralfs' type-form, but a variety. It is common 

 in England, but hitherto not found here. 



E. VENTRICOSUM, Lund. Plate XXXI, figs. 1-3. 



Large, twice as long as wide, outline subelliptic, deeply 

 constricted, sinus narrow linear; semi-cell trilobed, base 

 much dilated, polar lobe short somewhat dilated, incision 

 narrow linear, sides sinuate, two-lobed, superior lobe obtuse 

 tending upward, entire, not bifid in lateral view; basal 

 tumors three, intermediate two, and two in end lobe; in 

 vertical view elliptic, four undulations on each side; in 

 lateral view narrowed towards the ends, sides undulate, 

 apex subtruncate and dilated ; shows the superior lateral 

 lobule entire. 



Diameter 60-69 /<. ; length 105 }JL. 



Found this plant frequent in pond, Orange County, near 

 Maitland, Florida. Zygospores not infrequent as fig. 1. 



E. AMPULLACEUM, Ealfs. Plate XXXII, figs. 8-11. 



Semi-cells less in length than breadth, base inflated, not 

 emarginate, but having on each side, near the middle, a 

 small tubercle, or prominence ; end lobe exserted and di- 

 lated, its notch linear, or somewhat gaping. Membrane 

 minutely punctate. Transverse view, four inflations on each 

 side and one at each end. 

 Diameter 62-75 M- 



Xot as common as the preceding, but not rare. 



E. PURUM, Wolle. Plate XXIX, figs. 9-11. 



Small, short; semi-cells three-lobed, broader than long; 

 basal lobe much inflated, terminal lobe short, dilated and 

 notched ; in lateral view the base and end are more or less 

 inflated. 



Diameter 35-45 //. ; length 55-70 n. 



The smaller form from Florida, the larger from New Jersey. 



E. AFFINE, Ealfs. Plate XXVIII, figs. 11, 12. 



About twice as long as wide ; semi-cells three lobed ; basal 

 lobes somewhat emarginate ; intermediate between them and 

 the end lobe on each side is a prominence, the upper margin 

 of which is nearly horizontal : end lobe exserted, dilated, 



