170 WISCONSIN PHTTOPLANKTON 



per Turtle (r), Vermilion (rr), Waubesa (r), White Ash (sss), Whitefish (rr), 

 White Sand (rr), Wildcat (rrr), Winnebago (r), Wolf (s). 



A species that is almost universally present and one which varies 

 greatly in the character of the marginal cells. 



var. UNDULATUM Wille. PI. 46, Fig. 8. 

 Ofvers. Kgl. Vet.-Ak. Forh. 36, No. 5: 28. 1879. 



Sides of cells in contact with other cells undulate instead of straight. 

 (Tychoplanktont) . 

 Winnebago (rr). 



var. LONGICORNE Raciborski. PI. 46, Fig. 9. 



Akad. Umiej. w. Krakowie 20: 13. 1889; Printz, Skr. Vidensk. i Kristiana 

 Mat.-Naturv. Kl. 1913, No. 6: 74, pi. 5, fig. 149. 1914. 



Horns at the ends of processes much longer than typical form, some- 

 times swollen at apex. Cell wall smooth or granulate. 

 Diam. cells up to 40 p. Horns 12-30 ju, long. 

 Bone (rrr). 



Raciborski recognizes the forms glabrum and granulatum but,, judg- 

 ing by the variation in the nature of the wall in the typical form, these 

 forms should not be recognized. 



PEDIASTEUM KAWRAISKYI Schmidle. PI. 46, Figs. 10-13. 



Arb. d. Botan. Gartens zu Tiflis 2: 269. 1897; Nitardy, Beih. z. Bot. Cent. 32 2 : 

 164, pi. 5, fig. 5. 1914. 



Coenobia of 16-32-64 cells that are compactly arranged. Interior 

 cells 4-6 sided, sides straight. Inner half of marginal cells as interior 

 cells, outer half with two short projections that lie one above the other 

 when the coenobe is seen in surface view. Cell wall smooth. (Eu- 

 planktont) . 



Diam. cells 9-22 /*. Diam. 32-celled coenobia 60-100 /*. 



Big Bass (r), Palmer (rr), Tenderfoot (rrr), Winnebago (r). 



The cell shape is quite similar to P. Boryanum but the peculiar posi- 

 tion of the processes on the marginal cells at once distinguishes this 

 species from all others. Some investigators are inclined to the view 

 that P. Kawraiskyi is but a passing condition of P. Boryanum that is 

 found for one generation only. I have grown P. Boryanum in pure 

 cultures for several years and have never seen a single coenobe with the 

 projections of marginal cells lying one above the other, and so feel con- 

 fident that P. Kawraiskyi is not a temporary growth condition of 

 P. Boryanum. 



