NOCTURNAL HETOSE OE PLANTS. 
5 
general matter and requires first to be understood as a skeleton 
upon which the details are afterwards to be placed in order to 
give the body of the whole its fulness, its symmetry, its beauty, 
and its usefulness. 
The nocturnal influences upon the plant are, the withdrawal 
of the solar light, whether in the direct beams of the sun or the 
refraction and dissipation of them by the atmosphere ; a decrease 
of temperature, in as far as the direct beams of the sun are con¬ 
cerned always, and in the atmosphere according to temperature ; 
and a diminution of evaporation generally, with the formation 
of dew or humidity upon the substance of the plant in many 
cases. 
All these influences affect different plants in different ways, 
according to their natures, but this also is matter of detail and 
must be learned from an intimate knowledge of the natures of the 
plants themselves ; in fact, there is no royal road to the princi¬ 
ples of floriculture any more than there is to the practice, which 
is nothing but the application of the principles. 
Excepting for the refraction, which makes the actual presence 
of the sun a little greater than the absence, and causes the dawn 
to come before sunrise and the twilight to linger after the sun 
has set, and both of these increase with the latitude—every 
region on the surface of the globe has equal times of the presence 
and absence of the sun in the course of the year : the influence, 
as regards the whole year, is greatest at the equator, and a mi¬ 
nimum or 0 at the poles ; but the variation is affected by so 
many circumstances, that nothing that has been proposed can 
be made to agree with observation, thus the hottest summer is 
not immediately at the equator, but near the tropics; and some 
countries in pretty high latitudes which have the winter in¬ 
tensely cold have the summer as intensely hot. Upper Canada 
for instance has as hot a summer as the West India islands. 
These circumstances must be taken into account by the florist, 
for there are many plants of high latitudes that no winter’s cold 
will injure, and yet which require a stove to give them their full 
summer perfection. 
But though the time of the sun’s annual presence is nearly 
the same in all latitudes, the seasonal and daily distribution of 
