WISCONSIN PHYTOPLANKTON 105 



emarginate verrucae and below this a transverse row of rings or 

 masses of small granules the row forming a continuation of the 

 median row of granules of the processes. Vertical view elliptic, 

 with poles continued in straight slightly tapering processes termin- 

 ating in three divergent spines, lateral margins of processes crenulate 

 and with a single median row of granules ; sides of body of cells with 

 an intramarginal row of emarginate verrucae and a marginal row of 

 verrucae. (Facultative planktont.) 



Zygospores unknown. 



Cells 59-85 [x long with processes, 35-41 fx long without processes ; 

 breadth with processes 79-110 p., without processes 19-24 ju, ; breadth 

 at isthmus 9-12 ix ; thickness 12-13 /x. 



Bass (ss), Bear (rrr), Carroll (sss), Carson (rr), Crooked (sss), Des Moines 

 (rrr), Devils (r), Diamond (s). Hill (rrr), Horseshoe (sss), Howey (rr), Lindy 

 (ss), Meronk (rr), Pine (rr). Shell (sss), Silver (rrr). South Crab (rrr), Sun- 

 day (rr). 



The alga sometimes occurs in quantity in certain of the lakes. It 

 is distinguished from others of the same general type by the size, 

 divergence of the processes, and ornamentation. I have found that 

 the divergence of the processes is generally greater than W. & G. S. 

 West or Johnson figure but that this greater degree of divergence is 

 not caused by a curvature of the processes. The subapical ornamen- 

 tation of the body of the semicells is characteristic but subject to 

 considerable fluctuation. In some specimens the granules below the 

 emarginate verrucae are arranged in distinct rings, in others there 

 are two opposed arcs of granules, in still other examples these arcs 

 of granules are fused to form small arcuate verrucae. 



In some of the lakes the cells were consistently smaller than the 

 type and I have considered this a separate form. This form, parvmn 

 (PI. 79, Fig. 6), has the same general shape and ornamentation as 

 the type and differs only in the smaller size. Its length with proc- 

 esses is 42-68 [x, length without processes 25-31 fx ; breadth with 

 processes 62-68 fx, without processes 18-21 [x ; breadth at isthmus 9 //,. 

 Its distribution is as follows : 



Found (rrr). Horseshoe (ce), Lynx (r), Pine Tree (ss), Travis (ss). 



var. depauperatum var. nov. PI. 79, Figs. 7-11. 



Staurastrum leptocladum var. diver gens G. M. Smith non Wolle; Trans. Wis. 

 Acad. Sci., Arts & Lett. 19: 649. 1918. 



Semicells campanulate and with basal swelling less pronounced; 

 processes with the same kind of divergence as the type or with a 

 slight curvature ; apex of semicells with the subapical row of verrucae 

 and second subapical row greatly reduced ; bases of semicells without 

 transverse rows of granules, (Euplanktont?) 



