Algal Vegetation of Ponds on Hampstead Heath. 69 
The Protococcales. 
Of all the Protococcales, Chamydomonas occurs most frequently 
and often also in great numbers. It reached its maximum in the 
month of March in the years 1912, 1913, and also in 1914 : in each 
case following a period of considerable rainfall, and slightly rising 
temperature and sunshine. In ponds IV and VII Chlainydoniouas is 
sometimes accompanied by swarming cells of Cavteria, and the 
latter was found in the same ponds in December, 1913, almost to the 
exclusion of Chlainydoniouas. The Chlamydomonadaceae die out 
abruptly in April or linger until May, and in 1913, seemed to 
completely disappear until the following November. However, in 
one of the deeper ponds in 1912, a single record was obtained for 
July, and it is possible that some active individuals may persist even 
through the whole year in the deepest parts of the water. 
Goniuiu was most abundant from March to April, 1912, in April, 
1913, and was found but rarely again in March, 1914. It is there¬ 
fore a spring form but of distinctly later occurrence than the 
Chlamydomonadaceae. Pandorina is a fairly common an d Eudoriua 
an uncommon occupant of the ponds, only found from February to 
May, and much more abundant in 1912 than in 1913. Volvox has 
been found seldom, but in large numbers. It appeared in a deep 
corner of pond V which was constantly visited and dredged. On 
October 17th. 1912, the water from that part was green with Volvox ; 
this condition persisted until November 7th, when daughter colonies 
were frequent within the mother coenobia, but disappeared shortly 
after, and excepting for an occasional individual observed in the 
samples of the following January and February, no other records of 
this genus have been obtained, 
Of the remaining genera of the Protococcales, most were 
recorded in the year 1912. Tetraedou, Stipitococcus and Chlorochy- 
tvium were found in 1913 but have not been observed since ; Cavteria , 
Phacotus and Chcetosphcevidium have been frequently found in 1913 
and 1914 but were absent or (more probably) overlooked in 1912. 
Tetvaspova was unusually abundant in pond V in February and 
March, 1912, but has scarcely been seen since. Chavacium is never 
very abundant but has been found in June, 1912, and in November, 
1912 and 1913 on filaments of the larger species of Micvospora and 
Mougeotia. 
There is thus considerable variation in the behaviour of the 
different representatives of the Protococcales, but the majority are 
early spring forms attaining their maximum development in the 
