STUDIES OF BRITISH FRESHWATER' ALG^. 
31 
that, whereas during the winter months the temperature of the 
water is lower than that of the air, it is often the other way round 
in the summer. It is noticeable that only on three occasions did 
the temperature of the water exceed 20® C., so that the ordinary 
temperature of the water seems rarely to attain to the high summer 
temperatures characteristic of shallow ponds of this type ; the average 
summer-temperature, judging by the figures before us, appears to be 
about 17® 0. Attention may also be drawn to the following abnor- 
malities : — a strikingly low temperature on January 23rd, 1904 ; 
relatively high temperatures on May 29th, 1904, December 4th, 1904, 
May 13th, i906, and September 8th, 1906. Of the four years 1905 
was therefore most uniform as regards temperature. 
For the following table showing the monthly rainfall at Clifton 
we are, as already mentioned, indebted to Dr. Mill. The total 
annual rainfall is on the average (for the last 30 years) 35'45 inches, 
considerably more than half falling into the second half of the year. 
Special points calling for attention are the exceptionally heavy rain- 
fall during the last four months of 1903 and 1907 as compared with 
other years; very low rainfall in January and February, 1905; May 
and July, 1905; June, 1908 ; and September of 1906 and 1907. 
The total annual rainfall was as follows ; — 43‘65 in. in 1903 ; 
32-22 in. in 1904; 26.36 in. in 1905; 32-06 in. in 1906 ; 35-25 in. 
in 1907. Of these five years the year 1905 thus had considerably 
the lowest annual rainfall, the amount being about nine inches 
below the average. 
RAINFALL AT CLIFTON, GLOUCESTERSHIRE (ill inches). 
Month. 
1903. 
1904. 
1905. 
1906. 
1907. 
1908. 
Average 
for last 
January ... 
3-58 
•68 
4-95 
2-11 
1-76 
30 years. 
3-07 
February... 
4-09 
•86 
2-53 
1-81 
1-80 
2-44 
March 
2-17 
4-74 
2-81 
M4 
3-06 
2 28 
April 
2-29 
3-16 
1-36 
3-95 
3-04 
2-21 
May 
3-19 
•11 
2-56 
2-61 
1-87 
2-23 
June 
1-92 
4-28 
2-74 
3-23 
•71 
2-29 
July 
4-40 
•91 
1-35 
2-72 
2-18 
3-25 
August . . . 
4-39 
3-23 
4-11 
2-63 
2*34 
4-63 
3-61 
September 
3-33 
1-54 
1-33 
•82 
•62 
2-69 
3-35 
October ... 
8-03 
1-37 
2 03 
5-88 
5-33 
1-91 
4-01 
November 
1-91 
2-12 
302 
2-90 
3-11 
Ml 
3-53 
December 
3-13 
2-32 
1-13 
1-53 
6-28 
3-18 
0.— THE MORE IMPORTANT CONSTITUENTS OF THE 
FLORA (BOTH CRYPTOGAMIC & PHANEROGAMIC). 
The flora of the pond under consideration is certainly a rich and 
rather varied one, though subject to considerable fluctuations. From 
about March onwards till October or November floating aquatics 
