WISCONSIN PHYTOPLANKTON 45 



colony. Cells narrow, at least twice as long as they are broad. Cell 

 contents homogeneous; generally light blue-green, rarely grey. (Eu- 

 planktont). 



Cells 0.8-1.5 n broad, 2.5-4.5 p. long. 



Endophytic in sheaths of Coelospliaerium Kuetzingianum and Micro- 

 Cystis aeruginosa. 



Birch Island (r), Chetac (ss), Round (3) (rr). 



APHANOTHECE PRASINA A. Braun. PI. 5, Fig. 5. 



In Rabenhorst, Flora Eur. Algarum 2: 65. 1865; Cooke, Brit. Freshw. Algae, 

 218, pi. 88, figs. 3*-3i>. 1884. 



Colonies spherical to cylindrical, reaching a diameter of 3-4 cm. un- 

 der favorable conditions; bright green in color. Cells evenly dis- 

 tributed throughout the colony, broadly cylindrical and with rounded 

 ends. Individual cell sheaths confluent with the colonial envelope. 

 Cell contents homogeneous, bright blue-green. (Tychoplanktont). 



Cells 5-6.5 p broad, 7.7-11 /x long. 



Beaverdam (r), Nancy (rr), Pokegama (1) (rrr). 



The determination of this and the following species is open to ques- 

 tion since specific differences in these species are based in part upon 

 the macroscopic appearance of the colony when growing attached to 

 the substratum. The determination of plankton species is from imma- 

 ture colonies and must rest upon cell shape, size, and color. 



APHANOTHECE STAGNINA (Sprengel) A. Braun. PI. 6, Fig. 2. 



in Rabenhorst, Algen No. 1572; Cooke, Brit. Freshw. Algae 219, pi. 88, 

 fig. 4. 1884. 



Colony spherical, ellipsoidal, or cylindrical; generally macroscopic, 

 0.5-20 mm in diameter, pale verdigris-green. Cells broadly cylindrical, 

 their length never more than iy 2 times their breadth. Individual 

 sheaths of cells confluent with the hyaline, homogeneous, gelatinous, 

 colonial envelope. Cell contents homogeneous; pale to bright blue- 

 green. ( Tychoplanktont) . 



Cells 3-5 fj. broad ; 5-8 /* long. 



Lake of the Woods (rr), Whitefish (rr). 



GLOEOTHECE Nageli 1849. 



Colonies free-floating or sessile, of comparatively few cells enclosed 

 by a hyaline or variously colored, homogeneous, gelatinous envelope. 

 Individual sheaths of cells prominent, homogeneous or slightly lamel- 



