WISCONSIN PHYTOPLANKTON 103 



ture upon which Wille based his variety cornidum. My experience 

 with the alga in Ontario, New York and Wisconsin has been so similar 

 to that of "W. & G. S. West that I agree fully with them when they 

 say: "there can be no doubt that S. leptocladum always possesses the 

 two spines at the apex of the semicells, this was made the character 

 for a variety (cornutum) by Wille but we think it highly probable 

 that these spines had been broken off in the specimens originally de- 

 scribed by Nordstedt. All of the examples we have ever seen, from 

 many diverse parts of the world, possessed these spines, and it is 

 worthy of note that other observers only record the variety cornutum, 

 a fact which confirms our suspicions as to the invariable presence of 

 the apical spines in uninjured specimens." 



In some of the specimens that I have seen the transverse row of 

 granules on the basal swelling of the semicell was lacking, though 

 it usually is a conspicuous feature. 



var. DENTicuLATUM G. M. Smith. PI, 77, Figs. 10-14. 



Trans. Wis. Acad. Sci., Arts & Lett. 20: 351, pi. 11, fig. 14. 1922. 



Variety with the subapical spines replaced by a broad emarginate 

 elevation. Vertical view with the median portion of the lateral mar- 

 gins with a truncate elevation. (Facultative planktont.) 



Cells 79-95 ju, long with processes, 38-43 [x long without processes ; 

 breadth with processes 71-98 /x, without processes 18-21 /i; breadth 

 at isthmus 6-7 fx. ; thickness 10-12 /x. 



Balsam (s), Little Bass (rrr), Big McKenzie (c). Middle McKenzie (s), Oak 

 (rrr), Pokegama (c). 



var. iNsiGNE W. & G. S. West. PI. 77, Fig. 15 ; PI. 78, Figs. 8-11. 



Trans. Linn. Soc. 2nd. Ser. Bot. 5: 266, pi 17, fig. 17. 1896. 



Cells with the same general outline as the type, though with the 

 upward curvature of the processes more pronounced ; ventral margin 

 of the body of the semicells with crenulations or emarginate verrucae 

 extending from the base of the processes to the vicinity of the basal 

 swelling; dorsal margin with 4-6 emarginate verrucae that lie just 

 within the apex of the semicells and form a transverse row; center 

 of semicells with a circular protuberance. Vertical view rhomboidal, 

 with the median protuberance of the lateral margins truncate and 

 with the poles continued in long straight processes with undulate 

 margins. (Facultative planktont.) 



Cells 55-100 fx long with processes, 36-42 fi long without processes ; 

 breadth with processes 86-110 /x, without processes 20-26 ju,; breadth 

 at isthmus 6-8 /a ; thickness 15-18 /n. 



Blake (s), George (r), Lake of the Woods (rrr), Nieaboyne (rrr), Big St. 

 Germain (rrr). 



A variety which is unlike the others of the species in the subapical 

 ornamentation but which should be kept a variety of S. leptocladum 

 because of the characteristic curvature of the processes. 



