STUDIES OP BRITISH FRESHWATER ALG^. 
29 
many points of view involved in the investigation of this single pond 
that their complete elucidation would mean many years of detailed 
study. For the present we shall only attempt to give some idea of the 
life-history of the algal community that peoples the piece of water 
under consideration, and to indicate, as far as is possible, how this 
history is connected with seasonal changes and other external 
conditions. 
The general method of collecting the samples is described on p. 162 
— 163 of “Problems in Aquatic Biology,”^ and need not be repeated 
here. We, of course, fully recognise the defects that are bound to 
accompany the observations in a research of this kind, but inasmuch as 
most of our conclusions are founded solely upon positive data we think 
that the errors can probably be neglected. Each sample sent by the 
collectors was accompanied by useful data as to the temperature of air 
and water at the time of collecting, the nature of the weather during 
the previous week or fortnight, and the amount and appearance of the 
algal growth present, data, — which will frequently be referred to in the 
course of the paper. 
j5.— GENERAL CONSIDERATION OF THE PHYSICAL 
FEATURES OF THE POND AND OF THE 
METEOROLOGICAL DATA. 
The Fish Pond, Abbot’s Leigh, is an old pond situated not very 
far from Leigh Woods, near Bristol. The pond is of no very con- 
siderable size (maximum length about 70 metres, maximum breadth 
about 40 metres, and maximum depth about IJ metres), although 
big enough to render collecting from the middle parts difficult, the 
samples being therefore derived from what can be reached from the 
sides. The pond is situated on the Old Red Sandstone, but water 
probably also drains into it from the Carboniferous limestone. The 
pond is surrounded on all except the south side by fairly steep and 
wooded slopes of no great height ; on the south side water drains into 
it from an adjacent marsh. A small stream constitutes an outflow 
on the north side, while a pumping station (apparently very little 
used) is situated next to the roadway on the west side. The water- 
level is stated, as a rule, to remain practically constant. Shrubs and 
trees 2 extend down almost to the water’s edge and at many points 
cast a deep shade over the littoral vegetation in the summer and 
autumn, while in the late autumn a quantity of dead foliage is found 
in the pond — a certain amount being invariably present. This, 
together with the remains of the rather abundant Phanerogamic 
^Fritscb, loc. cit. 
2 Pine, Spruce, Beech, Oak, Ash, Elm, Hazel, and Hawthorn. 
