22 PLAtfT LIFE OK THE 



CHAPTER II. 

 NUTRITION (Continued). THE MACHINERY. 



Roots : their nature. Root-cap. Root-hairs. Root action. Absorp- 

 tion. Leaves and leaf action. Chlorophyll. Absorption of fluid 

 and gases. Leaf work by day and by night. Oxidation and De-oxi- 

 dation. Carnivorous plants. Transpiration. Circumstances pro- 

 pitious to it. The stem and its work. Its characteristics and vari- 

 eties. Buds. Branches. Tubers. Bulbs. Uses of the stem. As- 

 cent of liquids. Sap currents. 



Roots : Their Nature, Etc. So far as regards the ab- 

 sorption of those food materials derived from the soil by 

 the means above-mentioned, the root and its sub-divisions 

 are the agents through which the absorption takes place. 

 It is not necessary to allude to the various forms and 

 modifications of roots which form the study of the bot- 

 anist further than to say that their manifold differences 

 of form depend chiefly on the relative proportion that 

 the body of the root bears to its branches. If, as in a 

 " tap-root," like a carrot, the body is large, the branches 

 are small; if, as in the "fibrous root" of a grass, the 

 body is small, the branches are numerous and long. 



In ordinary language a great many things are called 

 roots which are not strictly so. For most people all parts 

 of the plant situate below the surface of the ground are 

 roots or portions of roots. Botanists, having regard 

 alike to the origin, mode of growth, structure, and uses 

 of roots, are enabled to define roots partly by positive, 

 partly by negative characters. Thus roots originate be- 

 neath the surface, that is from within the tissues of the 

 plant (endogenous), and force their way out through the 

 rind, as contrasted with branches and leaves which orig- 

 inate on the surface (exogenous). The extreme tip of 

 the root, and of its sub-divisions, is furnished with a mi- 

 nute " root-cap " of dead tissue pushed off from the tip 



