form blunt points, giving an appearance of nodular thickenings. 

 This may be interpreted as a modification of the nodule character 

 which is common to many species, and from the evidence at hand 

 it would seem logical to include O. gloeocystiformis with that section 

 of the genus characterized by the possession of polar nodules. Our 

 specimens compare more closely with the plant figured by Borge 

 ( 1906 ) than with those shown by Smith ( 1920 ) . 

 Among other algae in a few soft water lakes and swamps. Wis. 



Oocijstis lacustris Chodat 1897, p. 119; 1897a, p. 296 



PL 54, Fig. 1 



Plants usually in families of 2-8 within enlarged, oval mother 



cell walls; cells broadly elliptic or moniliform, the poles furnished 



with large nodular thickenings; chloroplasts 1-3 parietal plates, 



usually containing 1 pyrenoid; cells 12-20/a in diameter, 16-28/x long. 



Common in the plankton of several soft water lakes. Mich., Wis. 



Oocystis natans (Lemm. ) Wille 1911, p. 58 

 Cells ellipsoid with sharply pointed poles, without nodular 



thickenings, united in families of 8; cells 12-15/a in diameter, 23-26/x. 



long; chloroplasts 4-8 star-shaped plates. 



Typical plant not observed in our collections. 



Oocystis natans var. 7najor G. M. Smith 1918, p. 630 



PI. 54, Fig. 2 



A family of 2 or 4 ovate cells inclosed in the much expanded old 

 mother cell wall; poles of the cells rather sharply rounded but 

 without polar nodules; chloroplasts 4-8 in number, parietal, lobed 

 or star-shaped plates, each containing a pyrenoid; cells 16-25/x in 

 diameter, 31-38/x long; families about 90/a in diameter, 120;u, long. 



Plankter; common. Wis. 



Oocystis nodulosa West & West 1894, p. 15 

 PI. 54, Figs. 6, 7 

 Cells solitary, or 2 within old mother cell wall; ellipsoid to oblong- 

 ellipsoid, with rounded apices bearing a papillate thickening which 

 projects both inward and outward; 16-18/^ in diameter, 25-30/a long. 

 Rare; in plankton. Wis. 



Oocystis novae-semliae Wille 1897, p. 26 

 Cells ellipsoidal with thick walls; 4 or 8 individuals inclosed by 



the old mother cell wall; poles of cells without nodular thickenings; 



cells 5/i, in diameter, 8/x long. 



Typical plant not represented in our collections. 



[245 1 



