ALGOLOGICAL NOTES. U 



Here in Norway, many growing-places for freshwater Algae 

 which may yield more than hundred species, when surveyed, 

 contains so small quantities of water that they may freeze to a 

 solid ice-block in the winter, and the Algae may be exposed to 

 temperatures down to forty degrees centigrade below zero. I 

 think that the larger number of species must perish, and that 

 a re-immigration from larger bogs and pools is necesarry every 

 spring and summer. 



Only thorough and patient investigations in the Nature may 

 throw light on the many interesting problems concerned with 

 the ecology and biology of freshwater Algæ. 



IV. Resting Spores of Pediastrum. 



During the summer 1907 Professor Dr. N. Wille was collec- 

 ting Algae at Lyngør, a small fishing-village in South-Eastern 

 Norway. 



He then collected among other Algae a very interesting 

 resting stage of Pediastrum. Macroscopically the contents of 

 the bottle when dried op looked as red sand. — Under the 

 microscope it turned out to be resting stages of Pediastrum 

 and Coelastrum. The cells of the Pediastrum species were of 

 a strong red colour possibly owing to the presence of hæma- 

 ochrom. 



They contained a fat oil, and must be regarded as a resting 

 stage. The only other Algae which were found in the collection 

 were dead and empty cells of a Surirella- species. 



The resting form of the Pediastrum must be regarded as 

 an aplanospore in the sense of Wille, as the tight, red-coloured 

 contents were surrounded by a separate cell-wall. 



I took some of the material, and cultivated it in a pure 

 culture in a Petri dish, and in September 1919, the materia] 

 was germinated into normal Pediastrum colonies (fig. 17, PL I.) 



