Stillingfleet quotes from Aristophanes that “the crane points out the time of sowing” and the kite “when it is time to shear your sheep.” An old Swedish proverb tells us that “when you see the white wagtail you may turn your sheep into the fields; and when you see the wheatear you may sow your grain.” I have come across an English proverb: “When the sloe tree is as white as a sheet, you
must sow your barley be it dry or wet.” Miss Jekyll in her book Old West Surrey, speaking of the wryneck, quotes: “When we hears that, we very soon thinks about rining (barking) the oaks.”
There 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 temperature, in an irregular manner it is true, but sufficiently to be worthy of record. It has been said [237] that Thoreau, the American recluse and naturalist, knew the look of the country-side so intimately that had he been miraculously transferred to an unknown time of year, he would have recognised the season “within a day or two from the flowers at his feet.” If this is true, either American plants are much more businesslike than ours (which is as it should be), or else Thoreau did not test his opinions too severely, and this seems even more probable.
* This column gives Blomefield’s mean dates.