Algal Vegetation of Ponds on Hampstead Heath. 67 
Closterium, 2 spp. 
36 
Gomphonema ... 
40 
Staurastrum ... z. 
5 
Gyrosigma 
7 
Penium ... 
1 
Cocconeis placentula ... 
3+1 
BACILLARI7E. 
CYANOPHYCE7E. 
Navicula sp. 
61 
Osciliatoria 
25 
Tabellaria fenestrata ... 
56 
Nostoc ... . 
8 
Synedra radians ...» 
46 
Lyngbya... 
4 
j> sp# • • • . •. ) 
Phormidium sp. 
3 
Asterionella 
11 
Arthrospira 
2 
For convenience, the occurrence and distribution of these 
groups will be considered separately. 
The Flagellates. 
Synuva is undoubtedly the commonest of the Flagellates in 
these ponds. It has been found at times in every one of the series, 
but is always more abundant in those with standing vegetation. In 
pond V, in the region of decaying leaves of Poa Huitans, it has twice 
been found swarming in the samples collected (February, 1912, 
March, 1913) ; it disappears almost entirely in the summer months 
or may retreat to the deeper water where it would escape detection. 
Synuva is commonly associated with Dinobryon in ponds I, III and 
V, but the latter is never very plentiful: it also appears somewhat 
later in the season, and was unusually abundant in pond V in May, 
1913. 
Euglena has been observed sparsely at intervals in all the ponds 
and at any time of year, although more apt to increase rapidly in 
summer. In pond III, on June 18th, 1913, there was a sudden 
appearance of active Euglenae over the whole pond colouring the 
water a bright green. Eleven days previously, careful dredging had 
revealed no sign of any Euglena, and three days later no green 
colour could be detected although a fortnight later Euglena individuals 
were frequent in samples examined. Fritsch 1 concludes that the 
amount of dissolved substance in the water acts as a limiting factor 
to the Euglena observed by him in Barton’s pond; but in the month 
of June, 1913, there was a high rainfall 2 , and comparatively poor 
record of sunshine, so that this theory can hardly be applied to the 
case of the Hampstead ponds. 
1 Fritsch, F. E., and Rich, F. “ British Freshwater Algae in Nature.” 
Ann. de Biol, lacustre, VI, 1913, p. 64. 
1 Data of rainfall, sunshine, etc., were obtained from the Meterological 
Office for an adjoining part of Hampstead Heath. 
