here is something delightfully picturesque in the thought of man thus
helped and guided in some of his most vital operations by the proceedings
of the world of plants and animals, to whom that hard task-master Natural
Selection has taught so much.

I have gone through Blomefield's _Calendar_, recording for each species
the number of days between the earliest and latest known dates of
flowering. Thus the Mezereon did not flower earlier than 11th January or
later than 2nd February; this means that the date of flowering may, as
far as we know, vary to the extent of twenty-three days.

If we look at the recorded dates for all flowers appearing in February,
we find great irregularity. Thus _Daphne laureola_ has a range of
twenty-two days, whereas for _Vinca minor_ the figure is 114. The
average for February is 75.6, that for March is 55.6, for May 29.5, July
29.6. These figures suggest that the range of dates of flowering
diminishes as the temperature becomes less variable. But the variation
in summer temperature, though small relatively to the same factor in the
cold months, may nevertheless be sufficient to affect the flowering
habit. Yet there must be many factors in the problem of which we know
nothing. It is a curious little fact that the summer range should be
roughly one month.

Let us now consider my observations for 1917 as compared with
Blomefield's record of the mean date of flowering of the same species.

The most striking feature occurs at the beginning of April, when
Blomefield's observations are on the whole markedly earlier than my
record of corresponding facts. Of those noted by me as flowering in
April, one should have flowered in January, four in February, five in
March, six considerably earlier in April, and two slightly earlier in
that month.

In May Blomefield's dates are still mainly earlier than mine, in spite of
the fact that in this month the temperature was above the normal. In
June, on the whole (though with much variability), his dates do not
seriously differ from mine. In the first three weeks of June the
temperature was above the normal. In July, except at the beginning and
end of the month, my observations are clearly later in date than
Blomefield's, and during rather more than half of July the temperature
was below the normal. On the whole, and in spite of many doubtful
points, the difference between my results and Blomefield's seems to me to
be related to the curve of temper