III. 
ACCLIMATATION. 
THIS is a subject on which both practical and scientific men 
of the past and the present time have entertained opposite 
opinions. This may arise from different kinds of plants 
having been experimented on by different individuals. Al 
though all plants require a certain peculiar range of tempera- 
ture, moisture, light, and atmospheric pressure, which in some 
kinds cannot be greatly interfered with without proving fatal 
to their existence, yet the limits are very different in different 
tribes of plants; they are widest, as might be expected, in 
those whose native habitat embraces a wide geographical range. 
It has for long been supposed that the sensibility of plants 
may be diminished by habit, by gradation of climate, and by 
succession of generation. This theory will be found quite 
correct, generally, respecting ligneous plants, but it does not 
hold true with regard to agricultural crops, such as the cereals, 
which do not exist during the winter. Unfortunately, almost 
all the recorded experiments, that I am aware of, have been 
in relation to annual crops, or crops which are naturally of 
short duration, or greenhouse plants, the hardiness or tender 
nature of which was not previously well known. 
Among the greatest authorities for acclimatation we have 
Sir Joseph Banks and Dr. Macculloch. In advocating the 
hypothesis Sir Joseph relied upon the following case :—*In 
the year 1791, some seeds of the Canada rice-plant, Zizania 
aquatica, were procured from Canada, and sown in a pond at 
Spring Grove, near Hounslow. They grew and produced 
strong plants, which ripened their seeds. Those seeds vege- 
tated in the succeeding spring, but the plants which they pro- 
