Fresh Water Algae in Vicinity of Montreal 417 



1 cm. 100-200 micr. wide ; families 1 to 2 dm. 

 long. 

 Back River, Verdun, Bout de l'lle- 



Pediastrum Boryanum, Turp. 



Cells 4-64, 10-20 micr. wide, forming a continuous 

 circular disk, disk-cells 4-6 angled, marginal 

 cells bi-lobed, each lobe ending in a short obtuse 

 projection. 



Verdun, Mount Royal. 



P. constrictum, Hass. 



Cells of periphery irregularly 2-lobed, sinus nar- 

 row, lobes unequal produced into an obtuse 

 horn; central cells, polygonal. 16-32 cells. 



Verdun, Amherst Park. 



P. Ehrenhergii, Braun. 



Coenobium orbicular, composed of 8-16 cells or 

 quadrate of 4 wedge-shape cells, cells of peri- 

 phery cuneate, truncate at base, deeply bilobate, 

 lobes obliquely truncate, central cells polygonal, 

 yellow green. 



Verdun. 



Order IV. Ulothricaceae. 

 Family 1, Ulothricacege. 



Ulothrix variabilis, Kutzing. 



Filaments 5-6 micr. diam. cells cylindrical, %-l% 

 diam. long wall, thin, delicate, pyrenoid, single, 

 small. 

 Mount Royal, Bout de Tile. 



U. aequalis, Kutzing. 



Filaments 13-16 micr. diam. cylindrical cells 1-2 



diam. long. 

 Mount Royal, Verdun. 



