168 071 the Natural History of Vegetables. 



sprang. When, therefore, these descending vessels are low- 

 ered from their aerial station, and placed in immediate contact 

 with the objects of their search, viz. darkness and humidity, 

 they are impelled, or invited to burst through the bark the 

 nearest way to find them. 



Whether the powers of a root exist in its formation, or 

 from some internal faculty, which by expansion forms a vacuum 

 for the admission of extraneous qualities, is a curious question. 

 When considered as a member of a living being, whose head 

 elevated in the air, is constantly expanding and perspiring, 

 there is no great difficulty in comprehending how the fluids of 

 the root ascend to the head, and also how the vessels of the 

 root may be replenished. In this view, the fibrils and other 

 recipients of the roots may with propriety be called absorbents; 

 which implies, that there is a redundance of the necessary 

 quality without, and a want of it within, hence its absorption. 

 But this is not generally adopted ; some attributing the inhal- 

 ing power of the roots to a peristaltic motion of the vessels, 

 and the vitality of the plant, though we see the same effects 

 produced by a piece of lifeless sponge, or a bundle of unor- 

 ganised threads. It is necessary, therefore, to be cautious in 

 attributing to vegetable organisation, or any combination of 

 matter, self-agency. We are surrounded by the powers of 

 nature, mighty though invisible. The pressure of the atmo- 

 sphere and its constituent properties, the expanding force of 

 heat, the subtile effects of electricity, all more or less influence 

 vegetation, and unite with its own powers in its motions and 

 developement. 



Another circumstance, connected with the powers or suscep- 

 tibilities of roots, deserves notice : this is, their invariable ten- 

 dency to the place of their favourite or richest food. Whe- 

 ther this be heat, moisture, or manure, thither will all fibrils 

 advance, though placed at the distance of several feet. This 

 is explained, by supposing that the qualities mentioned are 

 surrounded by a little atmosphere carrying their specific pro- 

 perties, which reach, and in course attract, the fibrils. 



Of the Crown, or Vital Principle of the Root. — There is at- 

 tached to all roots what, from its position, is called their crown : 

 it divides them from the stem or stems, and consequently forms 

 a base to the latter. In the seed it was the heart or radius, 

 from whence arose, as has already been noticed, all the various 

 organisation of the plant. It is the seat of life in all trees, 

 especially when young, and remains long visible in some 

 kinds (the Spanish chestnut, for instance), even after the pith 

 and heart of the stem is gone to decay. It is always existent 

 in herbaceous plants, but becomes undistinguishable in most 





