WISCONSIN PHYTOPLANKTON 



117 



Fig. 15. Staurastrum limneticum Schmidle (x600). From plankton material 

 collected in Lake Victoria Nyanza, Africa. 



Cells 46-51 /i long; breadth with processes 100-130 ^u,, without 

 processes 28-36 jit; breadth at isthmus 14 /a (G. S. West). 

 Zygospores of the type unknown. 



Not found in the plankton of Wisconsin lakes. 



var. comutum var. nov. PL 82, Figs. 1-2. 



Staurastrum limneticum var. hurmense G. M. Smith non W. & G. S. West, 

 Trans. Wis. Acad. Sci., Arts & Lett. 20: 359, pi. 13, figs. 6-11. 1922. 



Cells shorter and narrower than the type; length about two and 

 a half times the breadth (without processes), sinus widely open and 

 with apex rounded, isthmus narrow; semicells with sides of bases 

 sublinear and processes upwardly divergent at apices but with bases 

 subparallel, ornamented with three or four rings of conical teeth 

 and ends of processes with three fairly long divergent spines, top of 

 semicell with subapical elongate bidenticulate verrucae. Vertical 

 view with length of processes one and a half times the diameter of 

 the cell, five- to seven-rayed, with the processes straight and orna- 

 mented as in the front view; body of the cell with a bidenticulate 

 verruca lying near the base of each process, verrucae forming a ring 

 within the margin of the body of the cell; processes of one semicell 

 alternating with those of the other semicell. (Euplanktont.) 



Zygospores spherical, with long slender spines that have their apices 

 bifurcate and the bifurcations recurved. 



Cells 48-52 ^i long ; breadth with processes 78-88 fx, without proc- 

 esses 20 jx ; breadth at isthmus 9 fx. 



Diameter of zygospores with spines 85-92 ju,, without spines 42-44 /x ; 

 length of spines 20-24 /a. 



Diamond (sss). 



This is a clearly defined variety in which there are strong argu- 

 ments for referring it to ^Si. rotula Nordstedt or to S. limneticum. 



