RIPENING OF FRUIT.

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that the evil effects occasionally produced by flowersin sleeping-rooms, are occasioned by a minute quantityof a volatile oil, to the formation of which the smell offlowers is to be attributed.

353. When fruits are first formed, they act very likeleaves ; they absorb food from the air, and under the in-fluence of light form organic matter, whilst at the sametime they collect and appropriate much of the organicmatter generated by the surrounding leaves. At thisperiod of their growth fruits have very little taste, andin composition they somewhat resemble leaves; whenthey have attained a certain size they undergo a newchange, and ripen, during which they acquire a sweet,or slightly acid taste.

354. In the first stage of the ripening of fruit, acidmatter is generated, in consequence, apparently, of theconversion of some of the tasteless constituents of the fruitinto malic, tartaric, and other organic acids. Duringthe second period of ripening the greater part of theseacids are converted into sugar, and a portion of colour-ing matter is at the same time formed. The formationof sugar and colouring matter takes place quite inde-pendent of the plant; for fruits may be ripened afterremoval from the plant which produced them.

355. In the first period of vegetation, when a seedhas been placed in the conditions requisite to germina-tion, the embryo plant has no power of obtaining foodfor itself, either from the air or the soil; it is entirelydependent on the seed for a supply of those matters