X he diatomaceous remains found in clays, sands and similar 

 deposits of the låter geologieal periods, liave recently become 

 of great importance in deciding the conditions under wliicli 

 tliese deposits were formed; whether in marine, brackish or 

 fresli water, and even in ascertaining the proportion of salt 

 contained in tlie water in which they were deposited. More- 

 over as the geographical distribution of the living species of 

 diatoms becomes well known, valuable indications may be 

 obtained from the presence of their remains, as to the cli- 

 mates that prevailed, while the formations which contain them 

 were being laid down. 



This however is not yet the case with regard to Sweden. 

 The recent diatomaceous flora of that country has been in- 

 vestigated only in the middle and southern parts, but the 

 boreal flora has not yet been studied. The only investiga- 

 tions of the arctic-boreal freshwater diatoms of Europé and 

 North America are those by Lagerstedt on the diatomaceous 

 flora of Spitsbergen and Beeren Eiland, and by P. T. Cleve 

 on the diatoms of Greenland. and Russian Lapland (The dia- 

 toms of Finland). No list of recent diatoms from Swedish 

 Lapland thus having been published, 1 accepted with pleasure 

 the opportunity of examining a number of about 40 gathe- 

 rings from Lule Lappmark, collected in 1883 by Prof. G. 

 Lageriieim and kept in the Riksmuseum of Stockholm, to- 

 gether with some samples from Gellivare (Nos. 43 to 47) col- 

 lected by Prof. V. Wittrock. Besides I have examined some 

 samples which Mr. E. Nyman had the kindness to gather 

 for me (Nos. 48 to 50, see below). 



The following is a list of the diff'erent localities in which 

 the samples were collected: 



