E. Marion Delf. 
THE ALGAL VEGETATION OF SOME PONDS 
ON HAMPSTEAD HEATH. 
By E. Marion Delf, D.Sc. 
[With Three Figures in the Text.] 
OR some years past, frequent observations have been made 
and recorded of the algal vegetation of a series of ponds 
on an estate known as Wylde’s Farm, adjoining Hampstead 
Heath. During this period the ponds have altered somewhat both 
in form and in depth, but this appears to have affected the phanero¬ 
gamic rather than the cryptogamic vegetation. The ponds are eight 
in number, and form a chain running from south to north : their 
bottom is a rich black mud, a foot or more in depth, with a subsoil 
of typical London clay; the water is somewhat chalybeate, for 
rusty masses containing numerous iron bacteria are often seen. 
The largest ponds are from 150 to 250 feet in length, and have a 
maximum breadth of about 50 feet. In the diagram (Fig. 1) the 
ponds are numbered for convenience. No. Ill has a length of 150 
feet and is 50 feet across at the widest part, and the others are 
drawn roughly in proportion. There is a drop in the land-level 
between some of the ponds, of some three or four feet: these 
descents (Fig. 2) are banked up with logs, and are often wet with a 
trickle of running water; they often bear algae, and are referred to 
as the “ cascades ” in this paper. 
Ponds I and VIII have been in existence for many years, a 
ditch formerly running between them ; and through this a more or 
less permanent stream of water ran, partly owing to an underground 
spring which supplied pond I even in very dry weather. In the 
winter of 1908—1909, the ditch was enlarged and banked up at 
intervals, the present series of ponds being thus formed in order 
to drain the surrounding fields which had been made over to the 
public. 
Occasional visits were made to the ponds in the years 1910 
and 1911, but no systematic examination was then undertaken. 
Considerable variety was found in the vegetation of the ponds. The 
commonest submerged flowering plants are Elodea, Callitriche, 
Lemna minor, Potamogeton spp. and Ranunculus aquatilis; the most 
characteristic marginal plants were species of Juncus, Bidens , Poa 
aquatica and Poafluitans. Amongst the algae, Spirogyra, Mougeotia, 
and Vaucheria were found in abundance in the months of February 
