CHAPTER III. 



GEOWTH BY THE ROOT. 



BOOTS LENGTHEir AX THEIE POnSTTS ONLY. ABSOBB AT THAT PAST CHTEI'LT, 



— ^INCEEASE ISr DIAMETBE LIKE STEMS. THEIR OEieiN. — ^AEE EEEDDfG 



OEGANS. — ^WITHOTTT ITTJCH POWES OF SELECTING THBIB. POOD. — l<rATTJEB 



OP THE lATTEE. MAT BE POISOITED.' — -AEE CONSTANTLY IN ACTION. — ■ 



SOMETIMES POISON THE SOIL IN "WHICH THET GEOW. HAVE NO BITIIS. 



BITT MAT GENERATE THEM. 



The root, being the organ through which food is conveyed 

 from the earth into the plant, is the part which is the soonest 

 developed. Even in the embryo, at the earliest commencement 

 of germination, it is the part immediately connected with the 

 root, that first begins to move, by lengthening all its parts, and 

 protruding itself beyond the seed-coats into the earth. 



But as soon as this primitive lengthening of the root has 

 taken place, and the upper part of the embryo, namely, the 

 young stem, has begun to exist as a separate organ, the root 

 changes its property, ceases to grow by a general distension of 

 its tissue, and simply increases in length by the addition of 

 new matter to its point. A root is therefore extended much in 

 the same way as an icicle by the constant superposition of layer 

 over layer to its youngest extremity, with this difference how- 

 ever, that an icicle is augmented by the addition of matter from 

 without, while the root lengthens by the perpetual creation of 

 new matter from within. 



For this reason, the extreme points of the roots are ex- 

 ceedingly delicate, and are injured by very trifling causes; 

 moreover, since all newly formed vegetable matter is extremely 

 hygrometrical, they have the power of absorbing, with rapidity, 



