The Development of Vegetation in the English Lakes. '177 



organisms, as recorded by the Wests or by the author. In view of the 

 doubts expressed by some continental authors as to the reality of Desmid 

 plankton — the percentage composition of the plankton is also given for 

 August 23-30, 1920, when comparative samples were taken from all the 

 lakes. These percentages are based on the number of individual organisms 

 or colonies, e.g., Splicerocystis, Eudorina, Tahellaria, etc. — the total number 

 counted for each lake was over 1000. By comparison with other countings, 

 these figures show rather low percentages of Desmids, and higher figures for 

 Diatoms, except in the cases of Windermere, Ullswater, and Esthwaite. 

 They are, however, the only figures available from collections taken at the 

 same time. 



Table VIII. — Percentage Composition of the Phytoplankton, August, 1920. 





cS 



is 



cc 

 OS 



Ennerdale. 



Buttermere. 



Crummock. 



Hawes Water. 



(D 



d 

 e> 

 is 



Ph 



D 



R 



Bassenthwaite. 



Coniston. 



Windermere. 



Ullswater. 



Esthwaite. 





14 



93 



25 



48 



19 



7 



1 



4 



11 



5 



7 





69* 



2 



24* 



21 



10 



4 



-5 



9 



8 



1 



5 



Filamentous CMoropliycesef 



7 



2 



18 



2 



1 



4 



6 



4 



6 



5 



1 





9 



1 



9 



1 



63 



82 



83 



52 



50 



31 



5 







1 



2 



23 



5 



2 



8-5 



2 



19 



30 



64 









13 



3 





1 







2 



27 



14 



Peridiniea 



1 



1 



9 



1 



2 





1 



26 



4 



1 



4 



* Almost entirely Spheeroeystis Schroeteri, Chodat. 



t Almost entirely Conjiigatse, especially sterile Mougeotia. 



A comparison of these results fully justifies the conclusions that — 



(1) The primitive lakes have a Desmid plankton in which Feridinium 

 Willei and Splicerocystis Schrceteri are abundant, and Diatoms inconspicuous ; 



(2) The more evolved lakes have a Diatom plankton in which, on the whole, 

 Ceratiuvi liirundinella and Eudorina elegans are more typical ; 



(3) The three most advanced lakes have in addition a considerable element 

 of Myxophycefe, at times dominant in Esthwaite. 



There is, therefore, a close similarity between the classification of the lakes 

 on this basis, and that already made upon physical and chemical grounds. 

 Since the characters of the plankton must depend very largely upon the 

 salient features of the lake waters, such a marked similarity is to be expected, 

 for it has already been shown that the properties of the lake waters are 

 dependent upon the degree of physical evolution of the lake. 



Y 2 



