122 



WISCONSIN PHYTOPLANKTON 



Cells somewhat smaller and with diameter of the cell greater than 

 the length of the processes. Processes trif urcate or bifurcate but with 

 much shorter spines. Chloroplast massive, with a broad lobe arising 

 opposite each side and sending a single ray into the two lateral 

 processes ; processes at angles with a single ray arising from the base 

 of the chloroplast. (Facultative planktont.) 



Cells 48 IX long with processes, 26 /a long without processes ; breadth 

 with processes 50 [x, without processes 24 fi ; breadth at isthmus 11 ix. 



Carroll (rrr), Horseshoe (rrr), Lake of the Woods (rrr). 



This alga as found in Wisconsin is identical with specimens from 

 the Scotch plankton. It is distinguished from the type by the shorter 

 processes and much shorter terminal spines of the processes. I have 

 found specimens in which all processes are bispinate and others in 

 which all are trispinate as well as intermediates between these two 

 extremes. 



57. Staurastrum furcigerum De Brebisson. PL 83, Figs. 4-7. 



in Meneghini, Linnaea 14: 226. 1840; G. S. West, Brit. Fresh w. Algae 172, fig. 



65G. 1904. 

 JDidymocladon furcigerus Ealfs, Brit. Desm. 144 pi. 33, figs. 12A-12D. 1848. 



Cells of medium size, length (with processes) slightly greater than 

 the breadth, deeply constricted, sinus acute-angled and with the apex 

 acuminate, isthmus narrow; semicells broadly hexagonal, with sides 

 bordering the sinus slightly convex and the apex flattened or faintly 

 concave; angles with two whorls of hollow processes, those of the 

 inferior whorl stouter and attenuated to a blunt end furnished with 

 three short divergent spines, body of processes with four to six con- 

 centric rings of small conical granules; processes of superior whorl 

 more delicate, not so strongly attenuated and ending in three small 

 divergent spines, ornamented with concentric rings of granules; 

 processes of inferior whorl parallel, processes of superior whorl sub- 

 erect to strongly divergent. Body of cell without ornamentation. 

 Vertical view triangular; sides somewhat concave and angles con- 

 tinued in gently tapering processes with truncate trispinate ends, 

 processes with concentric rings of granules; body of cell with three 

 smaller radiaUy arranged processes, one at each angle of the cell; 

 central portion of cell body without ornamentation. (Facultative 

 planktont. ) 



Zygospores spherical, furnished with numerous long spines that 

 have conical bases and bifurcate apices (G. S. West). 



CeUs 60-66 [x long with processes, 31-38 [x long without processes ; 

 breadth with processes 52-60 /a, without processes 28 fx; breadth at 

 isthmus 12.5-13.5 [x. 



Beaverdam (rrr), Des Moines (rrr). Duck (c), Granite (rr), Half Moon (rrr), 

 Hill (rrr), Lae Court Oreilles (rrr), Silver (rrr). 



