114 



WISCONSIN PHYTOPLANKTON 



rig. 14. Staurastrum ankyroides "Wolle (x500). From a plankton collection 

 made in Burned Eock lake, Ontario, Canada. 



processes strongly convergent, with the upper margin more sharply 

 erenulate than the lower margin, median area of processes with a 

 row of bifid verrucae at the base and simple spines at the apex, ends 

 of processes with three minute spines ; apex of semicells bearing sub- 

 apical emarginate verrucae. Vertical view quadrangular, angles 

 with long gracefully attenuated processes that terminate in three 

 spines, bases of processes with elongate bifid lateral verrucae and 

 apices with simple lateral spines, median axis of processes with a 

 single row of spines; body of cell with a conspicuous arcuate quad- 

 rigranulate verruca midway between every pair of processes. 



Zygospores unknown. 



Cells 60-68 fi long ; breadth with processes 92-132 jx, without proc- 

 esses 20-24 /x ; breadth at isthmus 11-13.5 /x. 



Not found in the plankton of Wisconsin lakes. 



var, pentacladum var. nov. PI. 81, Figs. 1-2. 



Semicells with five processes; processes of one semicell alternat- 

 ing with those of the other semicell ; apical verrucae on body of cell 

 more nearly semicircular and closer together. (Euplanktont?) 



Cells 120-150 jn broad with processes, 25-28 ju broad without proc- 

 esses ; breadth at isthmus 14 ]«,. 



Crooked (rrr). Little Doctor (rrr). 



The essential difference between the variety and the type is the 

 five-radiate character of the cell. I have collected the alga in con- 

 siderable quantity both in New York and Ontario (Canada) and find 

 it constantly four-radiate. On the other hand the few individuals 

 found in the two stations in Wisconsin were always five-radiate. 



The alga should be compared with 8. pentacerum (Wolle) G. M. 

 Smith from which it differs in the more elegant body of the cell, much 

 stouter lateral Verrucae on the processes, ornamentation of under side 

 of the processes, arcuate verrucae on the apex of the semicells, and in 



