WISCONSIN PHYTOPLANKTON 87 



siderable variation in the dimensions of the cells and I have found all 

 gradations from the typical variety to the form permagna of W. & 

 G. S. West (Z. c. 504, pi 7, fig. 14). 



var. PARVUM W. West. PL 73, Figs. 7-15. 



Jour. Linn. Soc, Bot. 29: 182, pi. 23, fig. 12. 1892. 



Cells much smaller; processes more delicate as in the variety 

 longipes but much shorter. (Facultative planktont.) 



Cells 20-50 [X long with processes, 14-27 ju, long without processes ; 

 breadth with processes 38-60 /x ; without processes 12-20 /a ; breadth 

 at isthmus 5-6 /x. 



Adelaide (ss). Big Bass (ss), Bloom (rrr), Bone (ss). Big Butternut (rrr), 

 Little Butternut (ss). Duck (ss), Dunham (rrr). East (rr). Granite (r), Hooker 

 (rrr). Long (rrr). Loveless (rr). 



26. Staurastrum protectum W. & G. S. West. 

 Ann. Eoy. Bot. Garden Calcutta 6=: 217, pi. 16, fig. 12. 1907. 



Cells fairly small, length about half the breadth (with processes), 

 deeply constricted, sinus widely open and with apex acute, isthmus 

 narrow; semicells broadly obversely triangular, with lower margins 

 straight and apex slightly convex, angles continued in divergent 

 processes of medium length; processes irregularly and finely granu- 

 late, terminating in two long divergent spines; apex of semicells with 

 four bidenticulate verrucae ; median part of body of the semicells with 

 two similar subapical verrucae. Vertical view triangular, with sides 

 slightly convex to slightly concave, angles with stout processes ter- 

 minating in two spines that usually do not lie in the same vertical 

 plane; median portion of each lateral margin with two bidenticulate 

 verrucae and central portion of body of the cell with a ring of similar 

 verrucae, two verrucae lying opposite each angle of the cell. 



Zygospores unknown. 



Cells 46 IX long with processes, 25 /x long without processes ; breadth 

 with processes 66 /x; breadth at isthmus 8.5 /x (W. & G. S. West). 



Not found in the plankton of Wisconsin lakes. 



var. PLANCTONicuM G. M. Smith. PI. 74, Figs. 1-4. 



Trans. Wis. Acad. Sci., Arts & Lett. 20: 355, pi. 12, figs. 8-12. 1922. 



Cells with stouter processes, granulation of processes concentric and 

 granules larger ; verrucae on sides of semicells lacking, apical verrucae 

 tridenticulate and forming a much smaller ring. Vertical view with 

 sides of cell strongly retuse. (Euplanktont.) 



Cells 36-89 /x long with processes, 25-28 /x long without processesfT' 

 breadth with processes 46-52 /x, without processes 30-34 ju, ; breadth ■" 

 at isthmus 6-7 /x ; terminal spines 5-6.5 /x long. ^^ T*^ 



Carroll (rr), Kudolph (rrr). h;:- ^''^ ^ 



\\^\^ 



W 



