II. 



The Freshwater Diatoms of the Canadian Arctic Expedition, 



1913-18 



By Charles W. Lowe 



This report is upon the diatoms found in the freshwater and brackishwater 

 collections of algae in general, no special collections being made for diatoms in 

 particular. 



The Bacillarieae is the one group of algae which is numerously represented 

 in all bodies of water, fresh or marine, and since these collections were made 

 so close to the arctic seaboard it is not surprising that a number of marine 

 forms were found in them. 



The conditions of life in the brackish ponds have been dealt with in the 

 report upon the freshwater algae and will explain how it is possible for freshwater 

 and marine species of diatoms to thrive in the same body of water. 



The samples collected differed greatly in the number of diatoms present; 

 in some they were very scarce and in others they were numerous. There was 

 such a mixture of plant and animal life in many samples that it was hardly 

 possible to separate the diatoms from the other organisms in order to properly 

 clean the diatoms with acids, before mounting them for examination. Also 

 there was not sufficient bulk of material for cleaning except in a few collections 

 from Teller, the warm creek near the Sadlerochit river, and from the big lake at 

 Bernard harbour. 



Many of the marine forms in the accompanying list were sent to Dr. L. W. 

 Bailey for identification or confirmation of identity, and the author wishes here 

 to acknowledge the kindness of Dr. Bailey for this help and for gifts of literature 

 upon diatoms. 



In addition to the literature cited in the report upon the freshwater algae 

 the following works were also consulted: 



H. Van Heurck . . Trait6 des Diatomees. 



Wolle The Diatomaceae of North America. 



and various papers by A. M. Edwards, L. W. Bailey, and others. The following 

 list gives the details of the species recorded. It represents 29 genera and 87 

 species and varieties. As is usually the case the genus Navicula has the largest 

 representation with 23 species. The classification used is that of Forti, as 

 modified by G. S. West. 



CENTRICAE. 



Melosibeae. 



Syndendriutn Ehr. 



Syndendrium Diadema Ehr. 



A few frustules of this marine diatom were found in a mud sample taken 

 from under the ice from the big lake at Bernard harbour, February, 1916. As 

 this is the only occurrence of this species in the freshwater collection I conclude 

 that it has been carried into the lake by wind or other means and was not really 

 living in the lake. 

 49069— 3f 



