well called _autumnalis_, gain from flowering in
August or September? Or again, what biological characters are there to
distinguish the plants flowering in June from those which do not show
themselves till July? It looks, to put the thing fancifully, as if a
parliament of plants had met and decided that some arrangement must be
made since the world would be inconveniently full if they all flowered at
once; or they may have believed that there were not enough insects to
fertilise the whole Flora, if all their services were needed in one
glorious month of crowded life. Therefore it was ruled that the months
should be portioned among the aspirants, some choosing May, others June
or July. But it must have been difficult to manage, and must have needed
an accurate knowledge of their own natural history. I must apologise for
this outbreak, and I will only add that this does seem to me an
interesting problem, namely, what are the elements in the struggle for
life which fix the dates on which plants habitually flower?

The most striking instance of the effect of the temperature is the
behaviour of arctic plants. {233} In Nova Zembla the summer consists of
two months, July and August, during which the mean temperature is about 5
degrees C. In these conditions, cases such as the following occur: at
Pitlekaj the last nine days of June showed a mean temperature of below 0
degrees C., while the average for the first nine days of July was between
+4 and +6 degrees, and on 10th July all the four species of Willow were
in full bloom, the dwarf Birch, _Sedum palustre_, Polygonum, Cassiope,
and Diapensia were in flower, and within a week the whole vegetation was
flowering. There was, in fact, a great rush or explosion of all sorts of
flowers as soon as the temperature rose: not that dropping fire which
begins with us with Mezereon in January and ends with Ivy in the autumn.

In the Arctic Regions temperature seems the absolute master, but in our
climate this is clearly not so. The best evidence of an inherent
tendency to flower on a certain date is that given by Askenasy {234} in
his observations on _Prunus avium_ (the Gean or wild Cherry). He
recorded the weight of 100 buds at regular intervals throughout the year,
and thus got the following results:--

_Grams_.
1st July 1 Period I.
1st August 2
1st September 3
1st October 4
1st November 4 P