COSMARIUM. 6$ 



diameter of 15 p. are not rare. These I consider undeveloped, 

 or young conditions of the plant evolved from zygospores. 

 Compare Introduction, p. 19. 



C. CONSTKICTUM, Delp. Plate LXI, figs. 1-4. 



Cells smooth, about one-half longer than broad ; deeply 

 constricted ; sinus acute-angled ; semi-cells near a three- 

 fourth circle, with inferior angles rounded ; end view oval ; 

 lateral view of cell an oblong with ends rounded and middle 

 constricted. Somewhat in character with C. Cucwmis, but 

 proportionately shorter. 

 Diameter 30-38 yw. 



Frequent in small ponds, New Jersey, Pennsylvania, etc. 



C. SCENEDESMUS, Delp. Plate LXI, figs. 7, 8, 9. 



Cells smooth, not as long as broad, depressed, constriction 

 deep, sinus narrow linear ; semi-cells subsemicircular, base 

 nearly straight, ends a depressed arch, angles rounded ; end 

 view elliptic ; side view circular. 



Diameter 32-38 p. 



Reminds strongly of D. Phaseolus, but has no reniform 

 base, and no central inflation. Sinus of fig. 7 too much am- 

 pliated. 



Occurs frequently. 



C. QUADRATUM, Ralfs. Plate XXI, figs. 8, 9, 10. 



Smooth, deeply constricted at the middle ; semi-cells in 

 front view quadrate, with a slight protuberance on each side 

 above the base, giving the sides a retuse appearance, angles 

 rounded; chlorophyl in larger forms usually divided into 

 two masses. 



Diameter, smaller form 20-23 ju. ; larger form 40 fit. 

 Ponds, Pennsylvania, rather rare. Minnesota. 

 The apices of the two forms differ ; the smaller ones are 

 more or less retuse, and the larger ones convex. The length 

 of each is twice the diameter. 



C. ANCEPS. Lund. Plate XXI, fig. 11. 



Small, full twice as long as broad, hexagonal- oblong ; sinus 

 narrow linear; side view oblong with sides slightly emar- 

 ginate; apices rounded: semi cells quadrate, rather longer 

 than broad, tapering moderately from base to end : end view 

 sub circular. Membrane smooth ; isthmus half the diameter 

 of the cell. 



Diameter 17-18 /<. ; Vngth 4o-"50 /u. 



