gg WISCONSIN PHYTOPLANETON 



Five or more processes on each semicell. 



Short processes with long terminal spines (55) S. irasiliense var. LundelUi 



Long processes with short terminal teeth. 

 Processes upwardly divergent. 



Cells of medium size (47) S. arachne var. curvatum 



Cells large (52) S. limneticum 



Processes subparallel to convergent. 

 Convergent processes. 



Verrucae on cell body conspicuous. . . . (49) S. arikyroides var. pentacerum 



Verrucae on cell body inconspicuous (47) S. arachne 



Subparallel processes. 



Cell body without verrucae (53) S. radians 



Cell body with verrucae. 



Only upper margin of processes crenulate (48) 5. pentacerum 



Both margins of processes crenulate. 



Processes with transverse rings of granules (51) S. rotula 



Processes with verrucae at base. (50) S. Opliiura 



C. Processes in two whorls. 



Vertical view triangular. 



Outline of processes smooth. 



Processes short (54) S. furcatum 



Processes long (56) S. tohopekaligense 



Outline of processes not smooth (57) S. furcigerum 



Vertical view circular. 



Superior whorl with four bifurcate processes (58) S. leptacanthum 



Superior whorl with six trifurcate processes (59) S. Arctiscon 



1. Staurastrum GRANDE Bulnheim. PI. 67, Figs. 8-9. 



Hedwigia 1861: 51, pi. 9, fig. 14. 1861; W. & G. S. West, Monogr. Brit. Desm. 

 4: 140, pi. 119, figs. 11-13, pi. 120, fig. 1. 1912; Carter, Ann. of Bot. 34: 308, 

 pi. 15, figs. 39-42. 1920. 



Cells fairly large, length equal to or greater than the breadth, 

 deeply constricted, sinus acute-angled, isthmus narrow; semicells 

 transversely elliptic, with dorsal margin more rounded than the 

 ventral, dorsal margin at times flattened at the apex, lateral angles 

 rounded. Vertical vieAv triangular, sides of cell body slightly con- 

 cave, angles rounded to acutely pointed. Cell wall finely punctate. 

 Chloroplast variable; with a small axial central mass and two large 

 laminate blades to each angle of the cell ; or without the central mass 

 and a parietal arrangement; pyrenoids normally seven, one in the 

 central mass and one in each blade, at times more numerous. (Tycho- 

 planktont.) 



Zygospores polygonal in profile, furnished with numerous stout, 

 curved to straight spines that taper to an acute point (W. & G. S. 

 West). 



Cells 68 IX long ; 60 jx broad at the base of the semicell, 28 fi broad 

 at the apex ; isthmus 14—15 ju, broad. 



Diameter of zygospores without spines 60 ju., with spines 100 /i 

 (W. & G. S. West). 



Bass (rrr). Devils (rrr). 



