244 = On the Times of Flowering of Early Spring Flowers. 
weather till Jan. 22nd, on which day was a heavy fall of snow, 
followed by a period of intense frost, which lasted unbroken to 
Feb. 18th, and with intermissions to the end of the first week in 
March. ‘The last half of March was mild. The mean tempera- 
ture of the quarter at Greenwich was only 85:2°. 
1896.—In December, 1895, the mean temperature at Green- 
wich was 40°2°, or 1:2° above the average. The four-feet ther- 
mometer at the beginning of January, 1896, stood at 44°5°. The 
weather during January and February was mild, dull, and dry; 
in March also mild and dull, but wet. The only period of con- 
secutive frost was for a few days towards the end of February. 
The mean temperature of the quarter at Greenwich was 42°2°. 
There is thus, as every one knows, a general correspondence 
between the meteorology of the season and the time of appear- 
ance of flowers; vegetation being forward in the mild first 
quarters of 1894 and 1896, and backward in the intensely cold 
season of 1895. I have tried, but without much success, to trace 
the connection more in detail. 
We may assume that the bringing of a plant into flower needs 
that it should have received a certain aggregate amount of energy 
in the shape of heat, either in the form of the sun’s rays, or of 
temperature of air, earth, and rainfall. We may also take it 
that each plant requires, in order that its vital processes may go 
on, a certain degree of temperature, different no doubt in diffe- 
rent species; but at least above 32° Fahr. in phanerogamous 
plants, at any rate. In the case of hardy plants, we may reckon 
degrees of temperature below the freezing point as nil, not as 
negative, i.e. growth is suspended, but not undone. For the 
sake of uniformity, I have taken the starting point as Jan. 1st, 
though doubtless in the earliest blooming plants the processes of 
growih which culminate in flower have been active before that 
date. On the basis of the above assumptions I have reckoned for 
some twenty species, of which I have the date of flowering re- 
corded in each of the four years 1893-96—A, the aggregate 
degrees of maximum daily temperature above 82° Fahr. ; B, the 
aggregate degrees of mean daily temperature above 32° Fahr. ; 
and C, the aggregate hours of sunshine recorded at Greenwich 
in each year between Jan. 1st and the coming of each species 
into flower; noting also the earth temperatures at four feet and 
at one foot deep. But, though I have spent a good deal of time, 
I have not discovered any close numerical relation between the 
date of flowering and either of these factors. To some extent 
apparently sunshine and air temperature may take the place of 
one another. One may see the snowdrop or winter aconite come 
into flower under the influence of bright sunshine when the air 
temperature in the shade scarcely reaches above the freezing 
point ; and, on the other hand, flowers will come out in mild 
