82 



KHNST OSTRl'I' 



Forms found in 100 samples or more. 



1 



2 

 3 

 4 

 5 



Characterising forms in 10 samples or more. 



Meridiem circularc 50 



Diatoma hiemale 43 



Synedra Ulna danica.... 41 



Melosirre sp. diversse.... 37 



Synedra Ulna typica .... 3(i 



(> I^pithoinia? sp. diverssc 



7 CymbellcC sp. diverse . 



8 Fragilaria? sp. diversae. 



9 Ceratoneis Arcus 



22 

 17 

 10 

 10 



This table shows lhat the forms most characteristic to the 

 Icelandic flora of fresh-water diatoms are: Meridion, Diatoma, Synedra 

 and Melosira. Comparing the two lists it further appears, lhat the 

 fact of a form being met with in a great number of samples not 

 necessarily means that it is generally characterising; for inst., Navicula 

 radiosa marked no. 2 in the first list only characterised two samples; 

 Cymbella venlricosa, Pinnularia viridis, fiomphonema subclavalum 

 each only one sample, while Pinnularia borealis and Hantzschia 

 amphioxys did not characterise any. 



