162 Kansas Academy of Science. 



72. R. convolutum (Corda) Rab. (A. convolutus Corda). 

 Plate III, fig. 21. 



Kansas: Douglas, August, 1915; Cherryvale, Decem- 

 ber, 1915; Coffeyville, November, 1915. 

 Iowa (4) ; Nebraska (24). 



2. Scenedestnus. 



Key to Species. 



I. Ends of cells acute, colonies of 4-8 cells, 5-27 by 3-9 mic. 



S. obliquus. 



II. Ends of cells rounded, terminal cells of series with long projections, 



colonies of 2-8 cells, arranged in a single series or in two alternating 



rows S. quadricauda. 



73. S. obliquus (Turp) Kuetz. (S. acutus Nageli). Plate 

 III, fig. 24. 



Kansas: Leavenworth, July, 1916. 

 Iowa (4) ; Nebraska (24) ; Missouri (11) ; Colorado 

 (15). 



74. S. obliquus var. dimorphus (Turp) Hansgirg. 

 Kansas: Lyndon, November, 1915, October, 1916; 



Paola, July, 1916. 

 Colorado (15) ; Iowa (4) ; Nebraska (24) ; Missouri 

 (11). 



75. S. quadmcauda (Turp) Brehisson; {S. cawdatMS ) Wolle. 

 Kansas: Atchison, August, 1915; Douglas, August, 



1915; Waconda Springs, July, 1916; Garnett, Au- 

 gust, 1916; Cherryvale, October, 1916. 

 Iowa (4); Missouri (11-9). 



76. S. quadricauda var. typicus Kirchner. Plate III, fig. 23. 

 Kansas: Osawatomie, August, 1915. 



Nebraska (24); Colorado (15). 



3. Coelastrum. 



Key to Species. 



I. Cells united by quite short processes, interspaces much smaller than 

 diam. of cell. 



A. Cells 5-12 mic. in diam. and somewhat lobed with truncate pro- 

 jection at the middle , C. cambt-icum. 



B. Cells 6-16 mic. in diam., spherical and united by the gelatinous 

 surfaces C. microporum. 



77. C. cambncum Archer. 



Kansas: Washington, August, 1916, July, 1916. 



78. C. micropoi-wtn Nageli. 

 Kansas: Douglas, August, 1915. 

 Missouri (11). 



4. Dictyosphserium. 



79. D. Ehrenbergianuyn Nageli. Plate III, fig. 25. 

 Kansas: Parsons, August, 1915, December, 1915; 



Paola, August, 1915; Lyndon, November, 1915; Cof- 

 feyville, July, 1916. 

 Missouri (11). 



Family III. Hydrodictyace^. 

 The only genus of the Hydrodictyaceae found was Pediastrum. 



Key to Species. 



I. Lobes of marginal cell simple, disk perforate P. duplex. 



