293 



Among these, more markedly, Pinnularia (to the extent of 

 25*^/0 in J. as against 5 ^/o in Z.), Eunotia (13°/o as against 1 ^/o), 

 ' Neidium (5 **/o as against 1 *^/o), and the rest with a difference in 

 percentage of less than 4. 



Only in J. : Frustulia (4 °/o), Melosira (3 ^/o) and Tetracyclus 

 (1 o/o). 



About as common in Z. as J. are Amphora and Diatoma 

 (each a little above 1 ^/o). 



The most striking faet in regard to the "peculiar forms" 

 is the great predominance which Jutland has over Zealand as re- 

 gards the two genera Pinnularia and Eunotia; the difference in 

 the percentage between J. and Z. being 20 and 12 respectively, 

 while for the most abundant genus in Z., Cymhella, it is only a 

 difference of 7 "/o between Z. and J. The "pecuhar forms" of the 

 genera Pinnularia and Eunotia are consequently very characteristic 

 of Jutland. 



If we now investigate the occurrence of the "peculiar forms" 

 in Z. and J. in reference to their different Tiabitats (cf. table on 

 p. 278) it will be seen, that the largest number of samples, both 

 from Z. and J., in which "peculiar forms" are found comes from 

 '■'■running water"" and from '■'■lakes and stagnant water^ and that 

 Jutland stands alone with respect to "peculiar forms" from heaths 

 and sandy districts. 



In Denmark I found in all 929 species and varieties, of which 

 621 are fresh water forms. 



Of the latter, Zealand has 410 and Jutland 449. 



Of the 410 forms from Zealand 77 (18.8 »/o) are "peculiar." 



Of the 349 forms from Jutland 116 (25.8^/0) are "peculiar." 



This shows that the peculiar forms are more common in Jut- 

 land than in Zealand. 



Moreover, of all the 621 freshwater-forms, 193 are "peculiar," 

 i. e. 31.1 per cent of the freshwater-forms found in Denmark are 

 "peculiar." 



Lastly, from Zealand I have 508 freshwater-samples, of which 

 95 (18.7 ^lo) contained "peculiar forms;" while from Jutland I 

 have 364 freshwater-sampleS; of which 188 (51.6 ^/o) contained 

 "peculiar forms." This proves that the "peculiar forms" of Jutland 

 occur more commonly in the samples from that place than in 

 those from Zealand. 



