ANNUAL PLANTS, SEEDS, SUGAR, &C. 49 



maturity of their fruit. But after August, the leaves form no more 

 wood, all the carbonic acid being employed for nutriment for the fol- 

 lowing year ; and, instead of wood, starch is formed and diffused by 

 the sap in autumn. The bark of such (aspens, pines, &c.) conse- 

 quently contains so much starch that it may be extracted, as from po- 

 tatoes, by trituration with water. The roots and other parts of peren- 

 nial plants also contain much starch, and sugar and gum are produced 

 from the starch in spring. The juice of the maple is no longer sweet 

 when its leaves, buds, and blossoms have become matured. The 

 branches of willows, contain much starch ; and when placed in snow 

 water, they produce roots several times longer than in pure distilled 

 water, in consequence of the greater quantity of ammonia in the 

 former. Part of the sugar of the cane disappears after it blooms, 

 and that of the beet root does not accumulate after the leaves are per- 

 fectly formed. 



Annual plants collect future nourishment in the same way as the 

 perennial, but they store it in their seeds in the form of starch, gum and 

 albumen, which are used by them in germination, for the formation of 

 their first leaves and radical fibres. The introduction through the 

 roots, artificially, of the same materials that plants use in the formation 

 of their organs by means of the leaves, destroys the plants, unless the 

 process of assimilation can take another form. Sugar, gum, or starch 

 are not therefore food for plants. Thus the production of blood in 

 animals is a vital function by their own appropriate organs, and these 

 admit of no artificial supply of that material. 



Seeds are composed of starch and gluten, in the quantities just suf- 

 ficient for the germ and radical fibre. The starch is converted into 

 sugar and the gluten takes a new form. Both being dissolved by water, 

 they "are conveyed to every part of the plant. This conversion of 

 starch into sugar is termed diastase, which is a new principle formed 

 at the beginning of germination : it contains nitrogen and furnishes 

 the elements of vegetable albumen. 



The sugar of maple trees is not formed in the roots, but in the 

 woody parts of the stem ; and the quantity increases until it reaches a 

 certain height, and remains stationary above. At the commence- 

 ment of vegetation a substance is formed which, being dissolved in 

 water, enters the trunk and converts the starch of the tree into sugar. 

 This is evidently greater than is used by the leaves and buds. Every 

 fibre and particle of wood is surrounded by a juice, while the starch 

 granules and sugar are enclosed in cells : these are supposed to be 

 formed simultaneously. The assimilation of substances generated in 

 the leaves depends on the quantity of the juices contained in the food. 

 When deficient, the substances which do not contain it, are separated 

 as excrement from the bark, roots, leaves, &c. The exudation of 

 gums and sugar by healthy plants is accounted for in this way ; and 

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