O* DESMIPS OF THE UNITED STATES. 



third of the diameter of the cell ; serai-cells with straight base, 

 angles rounded and sides convex, gradually converging. 

 Cytioderm granularly rough with one or two rows of larger 

 pearly granules near the margin, producing a dentate appear- 

 ance. 



Diameter about !<<> ft. (range from 62 to 112 ft.) 



Ponds, Pennsylvania, New Jersey, New York, South Caro- 

 lina, Rhode Island, Minnesota, etc. 



C. De Raryi, Archer. {Pleurotaemum oosmarioides, Do By). 

 Plate \V. fig. 5. 

 Cell- oblong, twice as \<>u>j :i- broad, with flatly rounded 

 ends; constriction narrow, straight, linear. Cytioderm smooth 

 or finely punctate; chlorophyl parietal. 

 Diameter "><>- :l <<.. length 104 1 1<> ft. 



Pomls, Berkshire Mountain-. Massachusetts 



C. Cuci mi-. Corda. Plate XV. figs. 6, 7, 8, 9 



Cells oval, one and one-half to one ami three-fourths times 

 longer than broad, ends broadly rounded; constriction linear; 

 cytioderm smooth ; chlorophyl covering the inside of the walls 



of the cell-. 



Diameter 16-56 ft. Thickness 36-40 ft. Isthmus about 



one-third of the diameter of the cell. 



Frequent from Maine to Florida. 



Besides the measures given, forme are found of much 

 '-mailer dimensions. Figs. 7, 8, 9 represent Buch ; every 



possihle si/.e from the largest t" the Bmallest, and down to a 

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

 or young conditions of the plant evolved from zygospores. 

 Compare Introduction, p. 19. 



C. CONSTRICTUM, Delp. Plate I,, figs. 1-1. 



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

 constricted ; sjnus aeute-angled ; semi-cells near a three-fourth 

 circle, with inferior angles rounded : end view oval ; lateral 

 view of cell an oblong with end< rounded and middle con- 

 stricted. Somewhat in character with C. Cucumis, but pro- 

 portionately shorter. 

 Diameter 30-38 ft. 



Frequent in smaller ponds, New Jersey, Pennsylvania, etc 



