274 FLOWERS AND FRUIT. 



small quantities, act powerfully on the animal sys- 

 tem. 



717. When fruits are first formed, they act very 

 like leaves ; they absorb food from the air, and under 

 the influence of light form organic matter, whilst at 

 the same time they collect and appropriate much of 

 the organic matter generated by the surrounding 

 leaves. At this period of their growth fruits have 

 very little taste, and in composition they somewhat 

 resemble leaves ; when they have attained a certain 

 size, they undergo a new change and ripen, during 

 "which they acquire a sweet, or slightly acid taste. 



718. In the first stage of the ripening of fruit, 

 acid matter is generated, in consequence, apparently, 

 of the conversion of some of the tasteless constitu- 

 ents of the fruit into malic, tartaric, and other or- 

 ganic acids. During the second period of ripening, 

 the greater part of these acids is converted into 

 sugar, and a portion of coloring matter is at the 

 same time formed. The formation of sugar and 

 coloring matter takes place quite independent of the 

 plant ; for fruits may be ripened after removal from 

 the plant which produced them. 



719. In the first period of vegetation, when a seed 

 has been placed in the conditions requisite to germi- 

 nation, the embryo plant has no power of obtaining 

 food for itself, either from the air or the soil ; it is 

 entirely dependent on the seed for a supply of those 

 matters which are necessary to its growth. A seed, 

 then, is a magazine, or store of food, prepared for 



