Problems in Aquatic Biology. 163 
attached or free-floating; sterile, flowering or fruiting, healthy or 
unhealthy. 
( b ) Amount of Algae present; attached or free-floating; 
healthy or unhealthy in appearance. 
(c) Temperature of water and air. 
(d) Changes in shading by surrounding plants and of muddi¬ 
ness of water. 
(e) Changes of water-level. 
(/) Animal life present. 
(g) General character of weather in preceding week or fort¬ 
night (wind, rain, temperature, sunlight). 
If these questions are carefully answered each time, one obtains 
working data of considerable value. The collection of what I call 
a representative sample is, however, also requisite to make such 
observations useful; a representative sample must contain all the 
different kinds of algal growth in roughly the same proportions as 
those in which they occur in the piece of water. As a rule the 
quantity of algal growth abstracted should be very small in amount, 
so as to avoid introducing a disturbing factor; in pieces of water 
with a poor vegetation, this disturbance is rather difficult to avoid, 
however, unless the flora be directly examined on the spot with the 
help of a travelling microscope. In collecting a sample the entire 
water must be carefully scanned, while the stems, leaves, etc., of 
Cormophytes and the surface of rocks must also be subjected to 
scrutiny; the method of algal collecting is, however, adequately 
described in all the leading text-books (West, Chodat, etc.) and 
need not be further dealt with. 1 No great knowledge of Algae, but 
care and precision are the requisites for making a good collection, 
Naturally the smaller the piece of water the easier is the gathering 
of a representative sample, and I have hitherto almost confined 
these investigations to small ponds. 
In illustration of some of the remarks made in the preceding 
pages and to show the mode of dealing with a series of periodical 
observations, I propose to discuss briefly the algal flora of a pond 
at Telscombe, near Newhaven, from which my friend, Mr. L. A. 
Boodle, F.L.S., was kind enough to collect a series of samples, 
unfortunately interrupted during my absence in Ceylon. The 
first samples were taken from this pond towards the end of 
December, 1902 ; at that time there was a rich algal flora, com¬ 
posed in the main of two filamentous species, viz. Oedogonium 
1 Cf. also Suggestions for beginning Survey Work on Vegetation. 
New Phytologist, Vol. IV., No. 4, April, 1905, pp. 101, 102. 
