40 WISCONSIN PHYTOPLANKTON 



(sss), Rice (1) (rr), Rooney (r), Sand (1) (ss), Sand (4) (IT), Shell (rr), 

 Silver (2) (ss), Travis (rr), Upper Turtle (ss), Waubesa (cc), White Ash 

 (sg), Wildcat (ss), Wolf (rr). 



var. MAJOR (Wittrock) G. M. Smith. PI. 4, Fig. 6. 

 Trans. Wls. Acad. Sci., Arts, & Lett. 18': 535. 1916. 



Mature colonies elongate; irregular, saccate, or clathrate. Colonial 

 envelope much firmer than in typical form and with larger cells. (Eu- 

 planktont). 



Diam. cells 5.5-6.5 /*. 



Center (rr), Mendota (ss), Nancy (sss), St. Croix (rr), Vermilion (cc). 



MICROCYSTIS INCERTA Lemmermann. PI. 5, Fig. 4. 



Abh. Naturw. Ver. Bremen 17: 342. 1903; Kryptogamenfl. d. Mark Branden- 

 burg 3; Algen 1: 76, 44, fig. 12. 1907. 



Colonies spherical or somewhat elongate, enclosed by a hyaline, homo- 

 geneous, and very delicate gelatinous envelope. Cells small, very close 

 together but equidistant from one another. Cell contents homogeneous, 

 without pseudovacuoles ; grey to pale blue-green in color. (Faculta- 

 tive Planktont). 



Diam. cells 1-2 p. 



Camp (rr), Chetek (r), Hooker (s), Prairie (r), Whitefish (rr), Winne- 

 bago (c). 



The cells of this species are very similar in appearance to those found 

 in Aphanocapsa elachista and A. delicatissima but their compact ar- 

 rangement shows that the alga is a Microcystis and not an Aphanocapsa. 



MICROCYSTIS PULVERA (Wood) Migula. 



in Thome", Flora v. Deutschl., Deutsch.-Osterr. u. d. Schw. 6, Kryptogamen 2, 

 Algen 1: 36. 1907. 



Anacystis pulverus Wood. Wolle, Freshw. Algae of U. S. 329, pi. 210, fig. 25. 

 1887. 



Colonies spherical or elongate, with a very delicate, hyaline, gela- 

 tinous envelope. Cells spherical, very closely crowded together and 

 forming a solid mass. Cell contents homogeneous, without pseudovacu- 

 oles ; grey, pale olive-green, or blue-green in color. (Facultative Plank- 

 tont) . 



Diam. cells 2-3 p. 



Browns (rr), Mill (rrr), Pardee (ss), Sunday (r), Winnebago (sss). 



Since the specific difference between this and the foregoing species 

 is mainly one of cell size it might be better to consider M. incerta a 

 variety of M. pulvera. 



