But the fruit must be eaten instantly; even an interval of a few minutes after it has been gathered is sufficient to destroy the charm; for, once severed from the stem, it rapidly acquires the temperature of the surrounding air.
Sufficient admiration has hardly been bestowed upon the marvellous power displayed by the vegetable world in adjusting its own temperature, notwithstanding atmospheric fluctuations,--a faculty in the manifestation of which it appears to present a counterpart to that exhibited by animal oeconomy in regulating its heat.

So uniform is the exercise of the latter faculty in man and the higher animals, that there is barely a difference of three degrees between the warmth of the body in the utmost endurable vicissitudes of heat and cold; and in vegetables an equivalent arrangement enables them in winter to keep their temperature somewhat above that of the surrounding air, and in summer to reduce it far below it.

It would almost seem as if plants possessed a power of producing cold analogous to that exhibited by animals in producing heat; and of this beneficent arrangement man enjoys the benefit in the luxurious coolness of the fruit which nature lavishes on the tropics.
The peculiar organisation by which this result is obtained is not free from obscurity, but in all probability the means of adjusting the temperature of plants is simply dependent on evaporation.

As regards the power possessed by vegetables of generating heat, although it has been demonstrated to exist, it is in so trifling a degree as to be almost inappreciable, except at the period of germination, when it probably arises from the consumption of oxygen in generating the carbonic acid gas which is then evolved.

The faculty of retaining this warmth at night and at other times may, therefore, be referable mainly to the closing of the pores, and the consequent check of evaporation.
On the other hand, the faculty of maintaining a temperature below that of the surrounding air, can only be accounted for by referring it to the mechanical process of imbibing a continuous supply of fresh moisture from the soil, the active transpiration of which imparts coolness to every portion of the tree and its fruit.