50 WISCONSIN PHYTOPLANKTON 



the polar lobe, in turn deeply incised, at times with both lobelets 

 incised; inferior lateral lobes usually with but a single deep incision; 

 all ultimate lobelets obversely spatulate and with their apices acu- 

 minate, truncate, or deeply emarginate. (Tychoplanktont.) 



Zygospores unknown. 



Cells 410 II long ; 450 fi broad in widest part, 74 /* broad at apex 

 of polar lobe ; 27 ju, broad at the isthmus. 



Lake of the Woods (rrr). 



This Desmid stands out from all others in its large size and in 

 the palmate nature of the semicells. Wolle's figures show that it 

 is exceedingly variable in the amount of incision of the lateral lobes 

 and in the nature of the ends of the lobelets. 



11. MiCRASTERiAs RADiATA Hassall. PI. 63, Figs. 1-3. 



Brit. Preshw. Algae 386, pi. 90, -fig. 2. 1845; W. & G. S. West, Monogr. Brit. 

 Desm. 2: 113, pi. 52, -figs. 1-4, 6-9. 1905; Carter, Ann. of Bet. 33: 300, pi. 20, 

 figs. 15-18. 1919. 



Micrasterias furcata Ealf s non Agardh, Brit. Desm. 73, pi. 9, figs. 2A-2B. 1848 ; 

 WoUe, Desm. U. S. Ill, pi. 35, figs. 5-6. 1884; Johnson, Bot. Gaz. 19: 58, pi. 6, 

 figs. 7-8. 1894. 



Cells fairly large, length usually slightly greater than the breadth, 

 very deeply constricted, sinus diamond-shaped, with apex acute and 

 outer portion somewhat convergent, isthmus narrow; semicells five- 

 lobed, polar lobe with basal portion oblong and upper portion some- 

 what dilated, angles of polar lobe continued in long slightly attenu- 

 ated divergent processes with deeply furcate apices, apex of polar 

 lobe somewhat concave ; lateral lobes formed by a deep, rather bluntly 

 pointed, lanceolate incision that extends half way from the periphery 

 to the cell nucleus, lobes divided by an acute-angled incision with a 

 rounded apex to form two lobules with subparallel sides and deeply 

 furcate apices. Cell wall smooth. Vertical view narrowly fusiform, 

 with poles acute. Lateral view of semicells narrowly cordate, with 

 apex rounded. Chloroplast extending into the lobules, portion in 

 polar lobe with apex entire, with two vertical ridges extending from 

 the polar apex to the nucleus, ridges of lateral lobes somewhat ir- 

 regular; pyrenoids 12-15, rather evenly distributed. (Facultative 

 planktont. ) 



Zygospores unknown. 



Cells 172-185 fi long ; breadth 142-165 fi, breadth at apex of polar 

 lobe 85-115 fi ; breadth at isthmus 18-21 ix. 



Beaverdam (rrr). Diamond (rrr), Horseshoe (rr), Kawaguesaga (rrr), Kim- 

 ball (rrr), Sunday (rr). 



W. & G. S. West have given a full nomenclatorial discussion of the 

 species and have shown conclusively why Ralfs' name is untenable. 



The deep furcation of the lateral lobes and the wide polar and 

 lateral incisions produce much narrower lobules than those of other 

 species which have the same type of incision. The species is subject 



