292 



(3 **/©), Amphipleura micans, Plagiogramma , Rhahdonema (each 

 to the extent of 2 "/o) and Pinnularia (1 *^/o). 



About as common in Z. as J. are Cyclotella, Gomphonema 

 and Rhoicosphenia (each to the extent of 2 ^lo). 



I have examined in all 1115 freshwater-samples, and "charac- 

 terising" forms are found in 593 (53.3 °/o) of these. Of coast- 

 samples I have in all 287, with "characterising" forms in 229 

 (80 ^/o) of them. Thls shows that the coast-samples are distinguished 

 to a far greater extent than are the freshwater-samples by the oc- 

 currence of "characterising" forms. 



Lastjy, in the table on pp. 267 — 68 I have given a list of the 

 Diatom-genera which I have found to be "characterising" in samples 

 which contained higher piants whose names were known to me. 

 These samples are few in number — only seventy-four, and I do 

 not think 1 can formulate any result worthy of mention. I may 

 however state that I found Achnanthes in seven of the eight Lernna- 

 samples, Cocconeis in six of the twelve Potamogeton-sdimples, and 

 in all the Hypnum-ssLmples (3). I doubt whether, on the whole, it 

 will be possible to demonstrate any correlation between certain 

 Diatom genera or species and the piants to which they are attached, 

 but if so, investigations of this kind must at any rate be carried 

 out according to a different plan from that which has prevailed 

 throughout the present work. 



By "peculiar forms" ^ (see pp. 273 — 77) I mean species or 

 varieties which I have found only either in Zealand or in Jutland. 



More common in Z. than J. are forms of the genera Cocconeis, 

 Cyclotella, Cymbellaf Epithemia, Fragilaria, Gomphonema, Navi- 

 cula, Nitzschia, Niizschiella, Stauroneis, Surirella and Synedra. 



Among these, more markedly, Cymbella (to the extent of 1 3 '^lo 

 in Z. as against 6 "/o in J.), Navicula (15 "/o as against 10 "/o), 

 and the rest with a difference in percentage of less than 4. 



Only in Z. : Hantzschia (4 ^/o), Cymatopleura, Diploneis, 

 Mastogloia, Niizschiella and Stephanodiscus (all to the extent of 

 2 ®/o or under). 



More common in J. than in Z. are Achnanthes, Anomoeoneis, 

 Caloneis, Eunotia, Neidiiim and Pinnularia. 



* "partikulære Former." 



