CHAPTER IV. 



FUNCTIONS OF THE ROOT AND LEAVES ORIGIN OF WOOD. 



172. In the preceding chapters we have described the various 

 organs, which compose the vegetable in its most perfect state ; 

 but we have considered them, with few exceptions, simply as 

 they present themselves to the eye, without supposing them pos- 

 sessed of life, or considering them in their combined actiou in 

 performing the various operations peculiar to organized beings. 

 We have seen, that the whole vegetable kingdom, however va- 

 rious in form and constitution, had its origin, at least, in minute 

 vesicles. We have also seen that all the organs of reproduction 

 and nutrition, are simple modifications of leaves. Who can foil 

 to admire the wisdom of that Being, who could construct with 

 materials so simple, the endless variety of vegetable organs, and 

 make them yield products of every variety, from the blandness 

 of water to the most powerful agents ; and to afford nutriment 

 to men and animals, and deposit contemporaneously and con- 

 tiguously the most virulent poisons ! 



Our next object is to consider plants as living beings, and so 

 far as possible to explain the various phenomena connected 

 with them as such. 



Section 1. — The Hoot. 



173. The first organ that appears in the germination of a 

 seed is the root. It bends downward, and soon commences 

 the proper functions for which it is intended, that of absorbing 

 nourishment from the medium which it penetrates, and giving 

 support to the plant. These seem to be the only functions 

 which the root performs. It lengthens by additions to its ex- 

 tremity, which always consists of cellular tissue, before de- 

 scribed under the name of spongiole. Through this extremity 

 the nourishment of the plant which is absorbed from the soil 

 passes. 



174. It has been thought that the root not only had the 

 power of selecting appropriate food for the plant, but also of 



173. What is the first or^im that appears in germination ? What tire its 

 functions? Where Joes the sap enter ?— 17-i. What power has the root 

 been supposed to have I 



