228 COMPOUND ORGANS OP PLANTS. 



atmosphere, the assimilation of the carbon and the evolution 

 of the oxygen, are processes which are greatly forwarded by 

 this agent. Now all these processes are just the reverse in 

 germination, for oxygen is absorbed and carbonic acid is elimi- 

 nated. It is not true that seeds will not germinate unless pro- 

 tected from the influence of light, since every day we see plants 

 germinating very well and with considerable rapidity, on fine 

 sponges, on sand, or other bodies from which they can imbibe 

 water ; but it is nevertheless true that a strong light will greatly 

 retard whilst darkness will favor the germinating process. 



The general phenomena of germination may be thus summed 

 up. When there are the suitable conditions of temperature, 

 air and moisture, the first phenomena which we observe in the 

 germinating seed is the swelling and softening of the envelopes 

 which covered it. These become distended with moisture, and 

 ultimately ruptured in a more or less irregular manner, as the 

 swelling of the seed increases. About the same time that the 

 seed commences to be distended with moisture, it attracts 

 oxygen from the atmosphere. This oxygen induces the formation 

 of the diastase, which acts on the starch contained in the coty- 

 ledons, converting it into dextrine and sugar, which dissolved 

 by water, are conveyed to all parts of the young embryo. The 

 bulk of this sugar is converted into carbonic acid, whilst the 

 remainder or dextrine, is organized into cellulose. Therefore, 

 instead of taking in the materials of nutrition from the earth 

 and atmosphere, or assimilating externally in germination as in 

 the process of flowering, the plant consumes these materials or 

 assimilates its own products. Now all the organs of plants, 

 whatever be their form, their nature, or their destination, have 

 for a base the same immediate principle, cellulose ; but starch, 



