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which are necessary to its growth. A seed, then, is amagazine or store of food, prepared for the use of the |
young plant, and accordingly a large quantity of the '
matters secreted by a plant are necessarily employed in jthe formation of seed.
356. There is a great distinction between organic andorganised matter. The former term signifies, as hasalready been explained, sugar, starch, or similar com-pounds ; whilst by the latter name is meant the cellular jand fibrous parts of plants. The chemist may by artifi- !cial means readily make some forms of organic matter, 1and convert them into others; but he cannot makeorganised matter: the latter is a product of vital action,and has never been formed by artificial means.
357. The first change effected by plants is to convert
carbonic acid and water, under the influence of light, jinto starch and similar forms of organic matter; the j
second operation is to form these substances into the j
various cells and tubes which compose the structure of tplants. The former is a purely chemical operation ; the 'latter requires something more, namely, the exertion ofvital power.
358. The embryo of a seed possesses vitality, but has j
no power, at first, of assimilating the elements of organic j
matter directly from the air; it is, therefore, able toconvert starch, gluten, and the other proximate principlesinto organised matter, and consequently grows and in-creases in size, by feeding on the store of organic matterprovided for its use in the seed.