VOL. XX. (i) 
FLOWERING OF PLANTS 
ii 
THE EFFECT OF THE COLD SPRING OF 1917 ON 
THE FLOWERING OF PLANTS. 
BY 
SIR FRANCIS DARWIN, F.R.S. 
(Read 19th February, 1918.) 
The following pages give the results of observations on 
the dates at which the commoner plants flowered at Brook- 
thorpe, near Gloucester, as well as the dates of a few other 
facts, such as the days in which the songs of birds were first 
heard. 
My observations began in April, 1917, originating in the 
obvious lateness of some of the vegetation. The record extends 
from April 1st to August 21st, and contains only 160 observa- 
tions, whereas in Blomefield’s Naturalist’s Calendar , 1 with which 
I have compared them, the number of recorded facts is much 
greater. I may express my indebtedness to the minutely 
accurate work of this author ; I only wish that my small 
contribution to his subject were more worthy of my guide. 
What interest my observations may possess depends on the 
fact that the Spring of 1917 was exceptionally cold. For this 
statement I rely on the weekly Weather Report of the Meteoro- 
logical Office, in which for each week of the year, the deviation 
from the normal temperature is given for a large number 
of stations in the British Islands. 2 I have taken as a standard 
the temperature at Clifton, which seems to be the station 
nearest to Gloucester. 
Now though the temperature has undoubtedly a great effect 
on the time of flowering, it is by no means the only element in 
1 A Naturalist's Calendar kept at Swaffham Bulbeck, Cambridgeshire. By Leonard Blomefield 
formerly Jenyns). Edited by Francis Darwin. Cambridge: at the University Press, 1903. 
1 I am also indebted to Mr. Embrey for his kind help in this matter. 
