ACCLTMATATION OF PLANTS. 
457 
"which he does, he ought to say, to try what 
are its powers of enduring cold, because that 
and that only can have to be tried ; it is worse 
than nonsense to talk of any change in the 
powers of the plant being attained. It is quite 
right to gradually bring the plant to its proper 
trial, and not to do anything suddenly, because, 
as we have shown, the oak itself might be 
reared in a stove and grow there, and would 
be killed if changed from thence to out-of-door 
growth in mid-winter. The nature of the 
plant is not changed ; but it is the same with 
plants as with animals — remove them from 
90 degrees to 30 degrees in the same hour, 
and mischief must ensue. 
The hardening off, as it is called, of all plants 
raised in heat, for planting in the open air, is 
quite requisite on all occasions, from the com- 
mon annuals to dahlias. All are in practice 
submitted to the same process : first, by ad- 
mitting more air than usual ; then by removal 
to a cooler situation ; lastly, perhaps to a cold 
frame which will merely keep out frost ; 
although these things are to be planted out in 
our warm spring months, as the temperature 
is increasing instead of declining. 
The reasoning of Mr. Johnson is good, and 
his advice is good, for on account of the much 
greater facility for cultivating hardy plants, 
the more we have capable of enduring our 
winters the better. " Hence," says the author 
of "The Principles of Gardening," "hence 
it is very desirable that an extended series of 
experiments should be instituted, to ascertain 
decisively, whether many of our present 
greenhouse and stove plants could not en- 
dure exposure to our winters if but slightly or 
not at all protected. It may be laid down as a 
rule, that all Japan plants will do so on the 
southern coast counties of England, but it re- 
mains unascertained to what degree of northern 
latitude in our island this genial power of en- 
durance extends? This last remark is in 
character with a practical man, for in truth 
that is the only inquiry to conduct : no 
possibility of changing the power of endurance 
exists ; all we have to do is to see what 
power the plant has, and there ends our task ; 
we can then assign the plant to its proper 
station. Mr. Johnson says, " We all know 
the larch was once kept in a greenhouse, and 
within these few months, such South American 
plants as Tropceolwm pentaphyllum and 
Gesnera Douglasii, have been found to sur- 
vive our winters in our garden borders." 
Very true; but the larch was no more a green- 
house plant for that fact, nor does the mere 
fact of surviving our winters in our garden 
borders, in Scotland and Suffolk or in 
Herefordshire, prove a jot towards the two 
plants being hardy. We remember very well 
seeing Tacsonia pinnatisUpula flowering on 
Twickenham Common, in front of a cottage, 
by the side of Tropceolwm aduncum, in 
the middle of January, yet the former is a 
tender plant, whatever the latter may be ; but 
the winter accommodated itself to the plant, 
not the plant to the winter. 
A registering thermometer alone can settle 
the question, as to how much frost the plant 
endures, or whether it endures any, and the 
thermometer ought not merely to be out of 
doors in the open air, but it should hang 
where the plant is ; for we have seen the 
dahlia in full flower in one place, and cut down 
to the ground in another, not one hundred 
yards off. And then again it has to be con- 
sidered, whether a sudden change has not 
done more towards killing a plant, than the 
intensity of the frost ; for it must be ad- 
mitted that rapid changes from heat to cold, 
and vice versa, do more mischief in our 
winters than the actual cold would, if it came 
gradually and went gradually. We think 
nothing of the mere fact of plants once 
considered tender being found hardy. Mr. 
Johnson says : " Another fact is, that many 
tropical plants, of every order and species, 
have been found to require much less heat, 
both during the day and during the night, 
than gardeners of a previous century believed. 
Other plants than those already noticed 
have passed from the tropics to our parterres, 
and even to those of higher northern latitudes. 
The horse-chestnut is a native of the tropics, 
but it endures uninjured the stern elements of 
Sweden. Aucuba japonica, Pceonia Mou- 
tan, we all remember to have passed from the 
stove to the greenhouse, and now they are in 
our open gardens." 
All this is very true, but it does not show 
that the nature of the plants or their powers 
of endurance have changed one degree, or 
even a shade of one. It is said further on : 
" Then, again, there is no doubt that all the 
Coniferae of Mexico, which flourish there at an 
elevation of more than 8,000 feet above the sea 
coast, will survive our winters in the open 
air. Among them are : Pinus Llaveana, 
Pinus Teocote, Pinus patula, Pinus Hart- 
wegii, Cupressus thurifera, Juniperusjlaccida, 
Abies religiosa, and some others." 
Perhaps the learned author will some of 
these days condescend to enlighten us rather 
more upon this subject, and inform us how 
there could be any doubt. The Pinus Lla- 
veana, Teocote, patula, and Hartwegii, are 
known hardy plants, and were introduced 
from Mexico as such, and we should like to 
know how they could be other than hardy 
from a climate like that experienced at the 
top of a mountain 8,000 feet high. 
The Coniferae of Mexico require no accli- 
matizing, as it is called. There can be no 
