l^Q WISCONSIN PHYTOPLANKTON 



1. Spondylosium planum (Wolle) W. & G. S. West. PL 86, Fig. 22; 



PL 87, Figs. 1-2. 



Jour. Linn. Soc. Bot. 40: 430, pi. 19, figs. 5-8. 1912. 



Cells under medium size, compressed, breadth slightly greater than 

 the length, moderately constricted, sinus widely open, with the apex 

 broadly rounded and the outer margin open, isthmus fairly narrow; 

 semicells oblong elliptic, with the ventral margin more rounded than 

 the dorsal, lateral margins very broadly rounded, with apices of semi- 

 cells flattened. Vertical view oblong-elliptic. Lateral view of semi- 

 cells subcircular. Cell wall smooth. Chloroplasts axial and with a 

 single pyrenoid. Filaments neither twisted nor enveloped in a gela- 

 tinous sheath; region of contact between adjacent cells very broad. 

 (Facultative planktont.) 



Zygospores unknown. 



Cells 12-18 /x long ; 12-22 /^ broad ; 7-12 /x broad at isthmus ; 8-10 /x 

 thick. 



Beaverdam (rr), Blue Gill (sss), Carroll (rrr), Catfish (rr), Clear Crooked 

 (rrr), Cranberry (ss). Crawling Stone (ss), Deer (rrr). Devils (r), Duck (rrr), 

 Dunham (rrr), Found (s), Horseshoe (rr), Lac Court Oreilles (r), Lake of the 

 Woods (rrr), Mercer (rrr), Middle McKenzie (rrr), Eeserve (r), Eock (rrr), 

 SheU (s), Whitefish (rr). 



The species is subject to considerable variation in the size of the 

 cells but the shape of the cells is a quite constant feature. It is a 

 species that has become widely distributed as a plankton organism. 



2. Spondylosium pulchrum (Bailey) Archer. PL 87, Figs. 3-4. 



in Pritchard, A History of Infusoria 4th. Ed., 724. 1861; Borge, Ark. for Botanik 

 15, No. 13: 72. 1918. 



Sphraerososma pulchrum Bailey in Ealfs, Brit. Desm. 209, pi. 35, figs. 2A-2B. 

 1848. 



Sphaerososrna pulchrum var. iiiftatum Wolle, Desm. U. S. 29, pi. 49, fig. 8. 

 1884. 



Cells large, compressed, breadth about twice the length, very deeply 

 constricted, sinus sublinear, with the apex acute and the outer mar- 

 gin very slightly open; semicells transversely elliptic, curvature of 

 the dorsal and the ventral margins the same, lateral margins very 

 broadly rounded, semicell apices with a conspicuous truncate eleva- 

 tion in the central region, adjacent cells of filament in mutual contact 

 only at truncate apical elevations. Lateral view of semicells sub- 

 spherical, with apex truncate and flattened. Cell wall finely punctate. 

 Chloroplasts axial, with 6-10 pyrenoids. (Facultative planktont.) 



Zygospores (of the variety Irasiliense) spherical, with smooth 

 walls (Borge). 



Cells 45-54 ix long with apical elevation, 38-45 /x long without ele- 

 vation ; breadth 76-83 fx ; breadth at isthmus 18-22 /x. 



Bass (rrr), Little Doctor (rr), NeU (s), Speese (rrr). 



