192 JVes/: Phytoplayikton of Eiiglish Lake District. 



the Protococcoideae, but no species of this order ever became 

 really common, although Sphcerocystis Schroeteri was the most 

 frequent. Botryococciis Braimii was only observed from August 

 to October, and then in very small quantity. 



The maximum abundance of plankton-Desmids occurs in 

 late September, or early October, in almost all the British 

 lakes,* and it is also the period of abundance of these Con- 

 jugates in the Httoral region and in the bogs. 



Bacillarie^. The Diatoms do not attain a universal 

 maximum at one definite period of the year, but the various 

 plankton-species reach their maxima at different periods. 



Melosira granulata has its maximum in April (temp. i.7°C.) 

 at the end of the cold period and the beginning of the vernal 

 rise of temperature. This is in general agreement with the 



MAR. 



0-4' 



APR. 



1-7° 



MAY 



JU. 



8-3° 



JY. 



a- 6' 



AUG. 



1^-7 



ccc 



cc 



XANTHIDIUM SUBH ASTIFERUM 



STAURASTRUM PARADOXUS 



ASTERIONELLA GRACILLIIMA — 



MELOSIRA GRANULATA 



ANAB/^NA LEMMERMANNM ooo< 

 CERATiUM Hf RUNDI NELLA ■»- + -t- 



FiG. 3. Chart showing the periodicity of six of the most abundant 

 constituents of the Windermere plankton from September 1907 to August 

 1908. The temperatures are in degrees Centigrade. 



* In the Schoenenbodensee Tanner-Fullemann {vide ' Bull, de I'Herb. 

 Boissier, 'VII., 1907) has recorded certain species of Desmids as occurring 

 in quantity in October. 



Naturalist, 



