s of observations on the dates at
which the commoner plants flowered at Brookthorpe, 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 1st April to 21st
August, and contains only 160 observations, whereas in Blomefield's
_Naturalist's Calendar_, {231b} 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 Meteorological 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. {232} 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 the problem. The first
plant on my list is _Ranunculus ficaria_, which I noted as flowering on
1st April, whereas in Blomefield the mean of seventeen yearly
observations is 28th February, the earliest date for this plant being
21st January, the latest 28th March. The extreme lateness of the
Celandine was doubtless due to the cold spring of 1917. But what are the
elements of the problem which fixed on this plant the general habit of
flowering early in the year?

In some cases we can see the advantages in early flowering. Thus the
average date on which the Hazel comes into bloom is 26th January, and
this, for a plant of which the pollen is distributed by the wind, may be
an advantage, since there are no leaves to obstruct the dispersal of the
pollen grains.

It may be answered that those Conifers which do not shed their leaves in
winter, _e.g._ the Yew or the Scotch Fir, are nevertheless
wind-fertilised. But this, though a point not to be forgotten, is no
argument against what has been said of the Hazel.

On the whole, however, we are excessively ignorant as to the biological
meaning of the dates at which plants flower. What advantage does the
orchis _Spiranthes_,