BIOLOGY OF PLANTS. 



etation during the summer, but store up large quantities for 

 the use of the plant, before it can derive it from a foreign 

 source in the spring. This process has been compared to 

 torpidity in certain animals, which store up a quantity of fat 

 in the autumn, from which they are nourished during their 

 winter slumbers. But the analogy is very slight, while the 

 chemical changes are quite different. The fat in the animal, 

 appears to combine with the oxygen in the lungs, a process 

 resembling the burning of a candle, by which the fat is slow- 

 ly consumed ; but the starch, which is laid up in the organs 

 of the tree, is converted into sugar, and in the spring is as- 

 similated. The process of assimilation is only delayed, until 

 the leaves are put forth, while in animals, no assimilation of 

 the stored matter takes place ; it simply burns out. 



The quantity of oxygen absorbed in all these cases must 

 also depend upon the fertility of the soil, and the quantity of 

 the gas contained in the air by which the plant is surrounded. 



The other parts of plants, such as the wood, petals, and 

 all those parts which are not green, absorb but a small quanti- 

 ty of this gas which is generally retained. 



The action of oxygen, according to the experiments of 

 Saussure, upon the fruit, during the progress of growth, is pre- 

 cisely similar to that upon the leaves. Fruits absorb oxygen 

 during the night, and give it off during the day. But the ex- 

 periments of Berard seem to indicate a different process, during 

 the ripening of fruits ; oxygen being absorbed, and carbonic 

 acid given off, both in the sun, and in the shade. This is 

 doubtless true ; for it is found, that green fruits, fully grown, 

 will not ripen in atmosphere deprived of oxygen, but will com- 

 mence the process on its admission, provided they do not re- 

 main deprived of it too long. Hence fruits may be preserved 

 through the year, by surrounding them with an atmosphere of 

 carbonic acid, or by excluding the air. By the process of ri- 

 pening, the animal matter, woody fibre, malic acid and water, 

 are diminished, and the sugar is increased. This would be 



