— 173 — 



The peculiarity that bristles are not found in this species du- 

 ring the winter has been mentioned. The thickest bristles are 

 found in the marginal cells; they seem to attain a thickness of 

 0-6 — 1*0 a. The other bristles are 0-4 p. or less. I have found 

 marginal bristles about 30 ju long and bristles projecting from the 

 junctions of the cells 48 fi long. 



I have not found this species otherwhere than in Bure Sø. 



Pediastrum duplex Meyen. Figs. 1, 9— 11. 



[Meyen 1828 pag. 772] [Lagerheim 1882 pag. 

 55] [Ghodat 1902 pag. 50, 227]. 



I have found bristles in several varieties 

 of this species, viz. both in the f. genuinum 

 A. Br. and the varieties clathratum A. Br. 

 and reticulatum Lagerh. and also in a very 

 characteristical variety of which I have not 



found any description in the litterature (Fig. 9). Fl J 9 - Pedia f um 



tf r v 53 } Meyen var. Tannic acid 



It is a genuine plankton-form, and resembles vesuvin. Reichert Homog. 

 the clathratum in the form of the spaces be- Imm - Vl2 ' Seibert 0c ' L 

 tween the central cells, but differs from it with respect to the cell- 

 wall, that is very rough and uneven also when the cells are very 

 young. 



Fig. 10. Pediastrum duplex Meyen var. clathratum A. Br. Löfflers method (X 730). 



