88 ORGANIC STRUCTURE. 



that which is moist. As the roots progress in length 

 they become divided and sub-divided into numerous 

 ramifications. Such roots are properly called fibrous, 

 not only because they are so at first, but because 

 their extremities are always so ; and though those of 

 trees become in time immensely incrassated towards 

 the collet whence they originated they are still con- 

 sidered and called fibrous. 



All plants are furnished with fibrous roots, but 

 under different modifications of size and duration. 

 Those of herbs are fugitive, in many cases annually 

 dying off in the autumn, and renewed in the follow- 

 ing spring ; of shrubs and trees the principals are 

 permanent, with annual growths of young fibres. 

 These principals appear to be only subterranean 

 portions of the axis or stem ; because in most cases 

 their components and structure are similar, except 

 that they have no pith ; in this respect only they 

 differ, both having concentric layers of perfect and 

 imperfect wood, a vital envelope, liber, and numerous 

 folds of bark; and in many instances both are furnished 

 with incipient buds, which, when developed on the 

 stem, are called shoots, but if from the root, are called 

 suckers. 



The natural direction of all roots is from dry air 

 and light, to moisture and darkness. The ascent of 

 the plumula or infant stem may be in general satis- 

 factorily accounted for ; but the contrary notion of 

 the rostrum, or first root, is not so easily compre- 

 hended. The latter is either repulsed by dry air and 

 light, or attracted by moisture. Whether in the 



