WISCONSIN PHYTOPLANETON 'J'J 



Cells about twice the size of the type, sinus acute-angled and with 

 an acute apex; semicells more narrowly elliptic and with the curva- 

 ture of dorsal and ventral margins the same ; spines at angles stout, 

 fairly long, and strongly convergent. (Tychoplanktont.) 



Cells 44-47.5 jtt long ; breadth with spines 62-72 jx, without spines 

 45-53 fi ; breadth of isthmus 12 /a ; spines 12-14 ii long. 



Beaverdam (rrr), Fish (rr). 



The dimensions of the alga as I have found it are those given by 

 W. & G. S. West for the plant as originally discovered in Madagascar 

 and not as they found it in North America. Like their North Ameri- 

 can specimens, however, the spines are strongly convergent and not 

 recurved. The specimens from Beaverdam Lake (Fig. 5) were 

 slightly smaller than those from Fish Lake (Figs. 3-4) but the stout- 

 ness of the spines and the open sinus show that they belong to the 

 variety and not to the type. 



16. Staurastrum connatum (Lundell) Roy & Bisset. 



Jour, of Bot. 24: 237. 1886. 



Staurastrum dejectum var. connatum Lundell, Nova Acta Eeg. Soc. Upsaliae 3 

 Ser., 8: 60, pi. 3, iig. 28. 1871. 



Cells small, length (without spines) about equal to the breadth, 

 deeply constricted, sinus widely open and acute-angled; semicells 

 obsemicircular, ventral margins rounded and apex slightly retuse; 

 superior angles submamillate and bearing a single straight fairly 

 short delicate spine, spines strongly divergent. Vertical view tri- 

 angular, sides of cells slightly retuse and angles rounded, angles with 

 a single short spine. Cell wall smooth. 



Zygospores unknown. 



Cells 22.4 iJL long without spines ; 21 /a broad without spines ; isthmus 

 6.6 /i broad; spines 8-13 /a long (Lundell). 



Not found in the plankton of Wisconsin lakes. 



var. rectangulum Roy & Bisset. PI. 70, Figs. 6-7. 



Jour, of Bot. 24: 237, pi. 268, -jig. 12. 1886. 



Sinus subrectangular and with a subacute apex; ventral margins 

 of semicells only slightly rounded and angles less mamillate. (Fac- 

 ultative planktont.) 



Cells 28 fx long with spines, 17.5 ix. long without spines ; breadth 

 31-32.5 fi with spines, 17 /a without spines ; breadth of isthmus 4.5 /x ; 

 spines 6-7.5 p. long. 



Pine Tree (r). 



The isthmus of the specimens that I have collected is less rectangu- 

 lar than Roy and Bisset show in their figure. The alga shows con- 

 siderable resemblance to ;S^. cuspidatum var. divergens Nordstedt but 

 the isthmus is far too short for 8. cuspidatum. 



