1G6 
Influence of Climate on Cultivation. 
of temperature or of manure hastens the flowering processes, 
while a high temperature or an excess of ammonia retards 
them. These effects form subjects well worthy of careful analysis 
in estimating the influence of climate on the growth of crops. 
A high temperature hastens the ripening of a plant after 
it arrives at a certain stage in its growth, but it has been 
generally overlooked that it has a. precisely opposite one on its 
early stages. A turnip or a wheat plant has comparatively little 
tendency to seed when sown on rich soil in the month of June. 
Both, however, run rapidly to seed unless highly manured when 
sown in March. All plants seed soonest in the poorest parts of 
a field. Cold nights have a great effect in developing the seeding 
of plants ; ammoniacal manures retard seeding by stimulating 
the growth of stems and leaves. Cold and drought then act to 
some extent in a similar way, by preventing plants from obtain- 
ing and appropriating a full supply of food. 
It is also worthy of being kept in mind that when the climate 
encourages early maturity, it also has the effect of producing a 
smaller yield. What is gained in time is to a certain extent lost 
in quantity. The rapidity with which any annual comes to 
maturity is not favourable to its productiveness. In those cases 
in which earlincss and productiveness do go togethei", liberal 
manuring must be resorted to. Manure is so far an equivalent 
for time. 
In conformity with this principle, the productive powers of 
wheat are greatest in moderately cool and moist climates. Under 
these circumstances the plant expands more fully. By retarding 
its flowering tendencies, its stems as well as ears are formed upon 
a larger scale, and it is capable of yielding more on a given space. 
For this reason tlie wheat plant attains about its maximum 
powers of production in Great Britain, in those districts where 
the climate favours its ripening. On the other hand the produc- 
tive qualities of wheat gradually decrease as the latitude lowers. 
As a general rule too — one that, so far as we are aware, docs not 
admit of any material excej)ti()ns — the latest varieties of crops are 
generally most productive when tlie supply of manure is moderate. 
'J'his is not so well exhibited in wheat as in some other plants 
which we shall have occasion afterwards to point out, but still 
we can tiace the principle distinctly enough. The longer the 
time that the leaves of any plant can present a green and fresh 
surface to the atmosjihere, the more can it not only rely on tiie 
atmospheric supjily of food, but the more food can it appropriate 
from the soil. 
The success which has in some few instances attended thin 
and early seeding of wheat is no doubt jiartly attributable to 
the lengthening of the period of growth. It exhibits in fact all 
