THE COTTAGE GARDENER AND COUNTRY GENTLEMAN, Mabch 26, 1861. 
In these rooms an egg was cooked quite hard in twenty minutes. 
But though plants have the power of preserving an internal 
temperature, differing from that of the external air in which 
they are vegetating, yet they have no more power than have 
animals to escape from the injurious excitement occasioned by 
being compelled to live for any protracted time in a temperature 
uncongenially elevated. In such a temperature, youthful and 
growing animals are stimulated to an excessive rapidity of 
growth, so attenuating, that nothing but removal to a colder 
climate can preserve them from premature death; and the 
same phenomena attend upon plants. These, over-excited by 
heat, acquire rapidly an unnaturally elongated growth, attended 
by a weakness of texture, that hastens them to decay, unless 
checked by a gradual reduction of temperature. The roots in 
such a heat absorb water with unnatural rapidity, and this is 
commensurately hurried through the sap-vessels of the stem and 
branches, so that the over-watery sap arrives at the leaves much 
too fast for them to elaborate it sufficiently, though an extra 
effort is made by preternaturally enlarging the leaves. The 
water transpired is excessive, but very little carbonic scid is 
inhaled, and consequently the quantity of carbon assimilated is 
very deficient. The whole structure of the plant is, therefore, 
watery and weak; and if a supply of water to the roots is with¬ 
held but for a few hours, the leaves wither and shrivel past 
revival. These organs not only lose the power to decompose 
carbonic acid, but also to decompose water, though the light to 
which they are exposed be the brightest sunshine; and thus 
deficient of carbon and hydrogen, the chief constituents of their 
colouring matter, they become unnaturally pale. 
It must not be omitted to be observed, that all plants have 
great capability of resisting the reduction, as well as the elevation, 
of their internal temperature, however low may be that of the 
air which surrounds them. In the polar regions, and even in 
those of less northern latitudes, they have to endure a tem¬ 
perature very far below the freezing-point of water—yet their 
sap is never known to freeze. If water does congeal in the 
texture of a plant it rifts it, but this never occurs unless ex¬ 
traneous moisture has penetrated through some wound or 
decayed part. We have seen trees so tom, but never without 
finding a mass of ice within the trunk or brancli traceable to 
some outward fissure. This is entirely in accordance with the 
experiments of Mr. John Hunter; and other experiments which 
we have tried, confirm us in acceding to the conclusion to 
which that distinguished anatomist, as well as Sprengel, Schubler, 
and others have arrived, that the sap of plants never congeals in 
the climate and soil of which they are native, however low the 
temperature to which they are exposed. Even in a temperature 
15° below that at which the sap, if taken from the tree, would 
freeze, yet, in the living plant, it remains uncongealed. This 
has been tried with the Vine, Walnut, Elm, and Red Pine. 
These experiments also determine that plants have but a 
slight power of generating heat; for the thermometer, placed 
within their stems, in winter sinks gradually nearly to the tem¬ 
perature of the exterior air; and in the spring or summer that 
instrument so placed does not follow implicitly the atmospheric 
variation; but this is not merely because wood is a bad 'con¬ 
ductor of heat. It is evident that a living plant has the power 
of preventing the congelation of its juices, and it is impossible 
to account for this phenomenon without connecting it with the 
plant’s vitality ; and we see no reason for concluding that plants, 
differing from animals, do not, during their respiratory function 
converting oxygen into carbonic acid, set free its latent heat, 
and thus preserve their temperature. It is beyond a doubt, 
that, by this chemical change, some plants at one period of their 
vegetation generate a considerable degree of heat. The stamens 
of Arum cordifolium emit so much heat at the time they shed 
their pollen, that twelve of them placed by M. Hubert round a 
thermometer raised the mercury from 79° to 143°. Under 
similar circumstances, M. Sennebier observed the stamens of the 
Arum maculatum were nearly 16° hotter than the surrounding 
air. The flowers of Caladium pinnatifidum, when emitting a 
strong ammoniacal smell, were observed by Dr. Schultz to be 
as hot as 81°, though the atmospheric temperature was but 
61 25 . The stamens of the Pompion, Pignonia radicans, and 
Polyanthus tuberosa have also been observed to elevate the 
mercury at the time of shedding their pollen, but in a much 
slighter degree. In every instance this evolution of heat is 
occasioned by a proportionate absorption of oxygen gas by the 
stamens and pistils at the instant of fecundation. The stamens 
of the Arum maculatum , for instance, have been shown by 
M. Saussure to absorb at that time two hundred times their 
bulk of oxygen gas, converting it into carbonic acid. 
Although some plants thus cause a great extrication of heat, 
and others are capable of resisting the greatest known cold to 
which they can be exposed, yet all have degrees of temperature 
most congenial to them, and if subjected to lower temperatures 
are less or more injured proportionately to the intensity of that 
reduction. If the reduction of temperature be only slightly 
below that which is congenial, it only causes the growth of the 
plant to diminish, and its colour to become more pale; this 
effect being in such case produced by the plant’s torpidity or 
want of excitement to perform the requisite elaboration ot the 
sap, as it is by over-excitement when made to vegetate in a tem¬ 
perature which is too elevated. If blossoms are produced at all, 
they are unfertile, and the entire aspect of the plant betrays that 
its secretions are not healthy and its functions are deadened. 
Mr. Enight says, that Melon and Cucumber plants, if grown in 
a temperature too low, produce an excess of female blossoms ; 
but if the temperature be too high, blossoms of the opposite 
sex are by far too profuse. 
If plants be frozen—and though some defy the attacks of 
frost, others are very liable to its fatal influence—death is brought 
upon them, as it is in the animal frame, by a complete breaking 
down of their tissue, their vessels are ruptured, and putrefaction 
supervenes with unusual rapidity. As already observed when 
considering the means of acclimatising plants, the more abun¬ 
dant is the water present in their vessels, the more apt are they 
to be injured by frosts ; whence the young shoots are often de¬ 
stroyed, whilst the older branches remain uninjured, and crops 
on ill-drained soils suffer more severely in winter than those 
where the drainage is more perfect. 
Deficiency of light is another contingency most influential 
in promoting the decline and death of plants. In proportion 
as they are deprived of this stimulus, they become unable to 
elaborate their juices, and, deficient in colour, weak, and of 
unnatural height, they die prematurely, and decompose more 
rapidly than those whose fibres, more firm and robust, are less 
combined with an excess of watery sap. 
Finally, the unhealthy vicissitudes to which plants, in com¬ 
mon with all other organised forms, are exposed, iuevitably 
bring upon them death ; and it would be mere waste of time to 
argue against those physiologists who maintain that, in favour¬ 
able circumstances, the life of plants may be prolonged in¬ 
definitely. Those who choose to surmise that some plants 
would endure throughout all time, if unfailingly preserved from 
all things offensive, and supplied without failure with all things 
agreeable, amuse themselves with imagining what would occur 
under circumstances of impossible attainment. 
A plant must be subjected to unfavourable contingencies ; and 
the greater the amount and frequency of their occurrence, the 
more speedily do they bring its life to a close—for the more do 
they aid chemical affinities in breaking down that resistance of 
their efforts which is the chief characteristic of vitality. 
So long as a plant lives it triumphs over those affinities. Its 
roots overcome the affinity of the soil and take from it its 
moisture; its leaves overcome the affinity of the atmosphere, 
and deprive it of the watery vapour it has in solution; the 
internal vessels overcome numerous affinities, and, by the de¬ 
composition of carbonic acid and water, perform within their 
simple tubes that which can only be effected by the chemist’s 
most powerful agents. These triumphs over chemical affinities, 
and that most characteristic of triumphs—its avoidance of 
putrefaction, endure in the same individual often for centuries 
of years; it is the most marked of the triumphs of vitality—its 
prime distinction as a creature, capable, for a time, of defying 
the laws which doom all organic matters to return to the dust 
from which they were created; for no sooner does that vitality 
cease, than the heat, the moisture, and the gases which vitality 
compelled to minister to the plant’s luxuriance and health, now i 
triumph in their turn, and serve to destroy that form which 
they had aided to sustain. 
That heat is necessary to putrefaction appears from the fact, 
that no vegetable matter kept at the freezing temperature of 
water will decay. Advantage of which is taken by the gardener 
occasionally to preserve his summer fruits and vegetables in the 
ice-house ; and Apples, Pears, and Grapes are borne unchanged 
half round the globe in the ice-ships which annually visit India 
from North America. 
That dryness effectually prevents vegetable putrefaction we 
see every day in the fact that our furniture does not decay; 
