34 TUFTS COLLEGE STUDIES, VOL. IV, No. 7 



not formed until after leaving the mother cell, 2-3 just below 

 each end, 7-26 /* long. Wis., G. M. Smith. Europe. 



5. L. LONGISETA (Lemm.) Printz, 1914, p. 60; Chodatclla 

 sub salsa var. longiseta Lemmermann, 1898, p. 310, PI. X, figs. 

 11-18. Cells ellipsoid, in vertical view circular, 8 /n wide, 12 /* 

 long, each end with 4-10 setae, 44-55 /* long. White Sand 

 Lake, Wis., G. M. Smith. Europe. 



MICRACTINIUM Fresenius, 1858, p. 236. 



Cells spherical or nearly so, solitary or loosely united in 

 colonies, cell with gelatinous envelope, bearing long, hyaline 

 setae, chromatophore bell-shaped, parietal, with or without 

 pyrenoid ; asexual reproduction by division in 2-3 directions, 

 the autospores escaping by an opening in the wall ; also by 

 akinetes. 



KEY TO THE SPECIES OF MICRACTINIUM. 



I. Cells mostly solitary ; setae uniformly distributed, cylindrical. 2. 

 i. Cells mostly in colonies; setae unilaterally placed, with thickened 



base. 3. 



2. Setae numerous, 25-45 j* long. i. M. radiatum. 



2. Setae few, about 16 M long. 2. M. f>ancisf>inosutn. 



3. Cells 3-7 M diatn., with 1-3 setae, about 60 n long. 3. M. f>usillui. 



3. Cells 6.5-10 M 'liam., with 4 setae, 23-40 /* long. 4. M. quadrisftuin. 



1. M. RADIATUM (Chodat) Wille, 1909, p. 57; Golcnkinia 

 radiata Chodat, 18943, p. 305, PI. III. Cells spherical, solitary 

 or in 4-celled colonies, 10-15 /* diam., with numi-rous setae, 

 25-45 M long, Fig. ii. Wis. G. M. Smith. l-.urope. 



2. M. PAUCISPINOSA (W. & G. S. West) G. S. West, 1916, 

 p. 198, fig. 124, F; Golenkinia paucispinosa W. & G. S. West, 

 1902, p. 68, PI. I, fig. 18. Cells solitary, spherical, 15-16/1 

 diam., with a few setae, about 16 p. long. Wis., G. M. Smith. 



I>< land. 



3. M. PUSILLUM Fresenius, 1858, p. 236, PI. XI, figs. 46-49 ; 

 G. M. Smith, 1916, p. 477, PI. XXV, fig. 18; Richteriella botry- 

 oidcs Lemmermann, 1898, p. 306, PI. X, figs. 1-6. Cells spher- 

 ical, 3-7 n diam., forming colonies of four cells in one plane, 

 each with 1-3 tapering setae, about 60 /t long. Wis., G. M. 

 Smith. t-.urope. 



4. M. QUADRISETUM (Lemm.) G. M. Smith, 1916, p. 479, 

 PI. XXV, fig. 17; Richteriella quadriseta Lemmermann. 1898, 

 p. 307, PI. X, fig. 7. Cells somewhat ellipsoid or ovoid, 6.5-7 X 

 7-10/1, each with 4 setae, 23-40 /i long. Wis., G. M. Smith. 



Europe. 



