Philosophy of Blancr.ing. 285 



because no green matter can be formed but by the action of 

 light; and if a part already green is kept for a long time in 

 darkness, it will become yellowish-white, in consequence of 

 all its green being destroyed by the peculiar action of the 

 atmosphere upon plants in darkness. This is the explanation 

 f blanching. But mere loss of color is not the only conse- 

 quence of plants being kept in the dark ; poisons, when it is the 

 nature of plants to yield poisons, are also formed in leaves by 

 the action of light ; the absence of this wonderful agent will 

 therefore prevent the formation, as well as the formation of 

 green color; and hence blanching renders poisonous plants 

 harmless. Thus, in the Celery, but a small portion onlyof the 

 leaves is exposed to light ; the whole of the stem and of the 

 lower part of the leaves is buried in the earth ; the small quan- 

 tity of noxious matter that might be formed by the few leaves 

 which are allowed to bask in the sun, has to pass down the 

 buried stalks of the leaves before it can reach the stem, where 

 it would be laid up ; but you know the leaf-stalk of the Celery 

 is very long, and any thing which has to filter from the upper 

 part of such a leaf to its bottom, has to take a long journey, in 

 the course of which it is constantly under the destroying influ- 

 ence of darkness ; so that before it can reach the stem, it will 

 all have perished. A similar effect is produced by the Italians 

 upon Fennel, which, although not a poisonous plant, has too 

 powerful a taste to be a pleasant food, except as an ingredient 

 for flavoring sauces. The Italians, in their warm climate, 

 cause Fennel to grow rapidly in darkness, and thus obtain 

 it in a state very like Celery in appearance ; the darkness 

 destroys the principal part of the flavor, no more of the Fennel 

 taste being left than is sufficient to give the blanched stems a 

 pleasant aromatic quality. — Lindley. 



