PLANTS AND THE ATMOSPHERE. 431 



seed may preserve, for a longer or shorter period, tlie essential principle of life, 

 A little heat commences the evolution, and from that moment organic matter, 

 absorbed by the infant tissues and borne thither by cells which are then formed, 

 takes its place in the organ which it constitutes. During all this time, the plant 

 and the animal live upon their own private store, taking nothing fi-om without, 

 and, to complete the analogy, consume a portion of their own substance. Sooo, 

 when all this is exhausted, the animal being formed is ready to live, as the plant 

 assuming a shape is to vegetate, and at the same instant, a necessity common to 

 both is apparent; that, namely, of finding nourishment from without. From thi s 

 time, however, all analogy ceases, and the separation of the two kingdoms com- 

 mences. The plant creates and reduces, the animal destroys and oxydizes. 



Let us pursue these analogies. In every expanding flower, botany points out 

 to us the organs of the two opposite sexes which contribute, each in its own 

 character, to the fertilization of the ovary. JSTow, at the very moment when the 

 flower seems to borrow the sexual function of reproduction which was considered 

 to be the exclusive privilege of animuls, it imitates them still more in consuming 

 organic substances by active respiration, " All flowers," said Priestley, " constantly 

 exhale a deadly gas during the day as well as at night, both in light and dark- 

 ness." Daily experience confirms this assertion, and De Saussure has shown that 

 this poisonous gas is carbonic acid. Finally, one of our most justly celebrated 

 chemists, M. Cahours, bas, in a recent and complete work, studied all the circum- 

 stances of this respiration of flowers and fruits. 



If it be true that this combustion of organic matter, this expenditure and loss 

 of force, are necessary to accomplish the act of fertilization in itself, it is, above 

 all, in the sexual organs that they ought to be produced. Experience, in fact, has 

 confirmed this view, and it has been discovered that the stamen or male organ is 

 most active in its expenditure. This imjDortant fact does not stop there. All 

 combustion evolves heat : it is to their respiration that animals owe their high 

 temperature, and it is of the utmost necessity that the stamens and carpels should 

 become heated since they breathe. The question was, to find thermometers 

 sensible enough and a suitable plant. The first plant to permit of the height of 

 temperature being ascertained, was the pumpkin which had never been suspected 

 of preserving such heat. Its flowers being large, air-thermometers are easily 

 introduced into them ; some of them are male and others female flowers, the 

 latter of which shewed themselves much more cold than the former. 



However, gourds, melons and pumpkins become warm to a very small extent, 

 and may be said, to resemble cold-blooded animals ; the plants that imitate warm 

 blooded animals are those of the Arum family. One of them, the Arum macur 

 latum, found abundantly in the hedgerows, is enveloped by a folded leaf which 

 encloses the flower within a small compass and hinders the heat from being dis- 

 persed in space. This is the singular phenomenon observed by Lamarck, Senne- 

 bier, Bory de Saint Vincent, and by Saussure himself. Habitually, the Arum 

 is cold, but, at a given moment, which must be watched for and which the exper- 

 imenter must know how to take advantage of, the plant rises from 7 to 8 degrees 

 above the temperature of the atmosphere, Hubert, a very sagacious observer, 



