WISCONSIN PHYTOPLANKTON 11 



var. KLoxGATuw W. & G. S. West. PI. 53, Pig. 2. 



MonogT. Brit. Desm. 1: 168, pi. 21, figs. 14-16. 1904. 



Cells veiy much longer and with curvature confined to the apical 

 regions. (Tyclioplanktout.) 



Length 418-480/^; maximum breadth S/u,; breadth near apices 

 5-8 /It. 



Little Basa (m), Pokegama (it). 



6. Closterium aciculare T. We.st. 



Trans. Micr. Soc. London N. S. 8: 153, pi. 7, fig. 16. 1860 (in Quart. Jour. Micr. 

 Sci. 8: 1860). 



Cells greatly elongated, length many times the breadth; median 

 portion narrow and straight, terminal portions curved; very gradu- 

 ally attenuated to acutely rounded apice.s. Cell wall colorless; with- 

 out a median girdle; smooth. Chloroplast with an axial row of 6-8 

 pyrenoids. 



Zygospores unknown. 



Length 500 jii; greatest breadth 5 /x (T. West). 



Not found in the plankton of Wisconsin lakes. 



var. suBPRONUM W. & G. S. West. PI. 53, Fig. 3. 



Mouogr. Brit. De.sm. 1: 175, pi. 23, figs. 4r-5. 1904. 



Cells longer and with attenuation of terminal portion more deli- 

 cate. Chloroplast extending half way from cell center to cell apex. 

 (Facultative planktont.) 



Length 540-610 /x ; breadth 7.5 fi. 



Browns (r), Green (r), Meudota (r). 



7. Closteriusi acutum (Lyngbye) De Brebisson. PL 53, Fig. 4. 

 in Ealfs, Brit. Desm. 177, pL 30, figs. 5A-5E; pi. 34, fig. 5. 1848. 



Cells small, generally curved, rarely straight; very gradually at- 

 tenuated to subacute or rounded apices. Cell wall colorless ; without 

 a median girdle. Chloroplasts without longitudinal ridges and with 

 an axial row of 2-4 pyrenoids. (Tychoplanktont.) 



Zygospores oblong, with ends very deeplj' emarginate and sides 

 slightly convex; angles rounded and forming projections that lie 

 parallel to the long axis of the zygospore (Ralfs). j 



Length 177 n ; breadth 3.75 [i. |-" 



Length of zygospore 43 /x; breadth of zygospore 13 ju, (Ralfs) 



Green (rrr). 



8. Closterium Ralfsii De Brebisson. 



in Jenner, Flora of Tunbridge Wells X. 1845 (Ref. Nordst. Index De8m.) ; in 

 Ealfa, Brit. Desm. 174, pi. 30, figs. 2A-2B. 1848. 



Cells large, length 6-8 times the breadth, somewhat curved, arc of 

 curvature of outer margin about 45°, inner margin tumid in median 

 portion ; more sharply attenuated at extremities and with apices 



