THE ROOTS OF VASCULAR PLANTS. 225 



particular in leaves of a firm texture, such as those of 

 the Orange, Ficus elastica, &c. By this property we 

 are sometimes enabled to multiply these species. 



Section V. 

 Of the Functions of Roots. 



The functions essentially peculiar to roots are — 1st, to 

 absorb nourishment; 2d, to fix the plant to the ground. 

 The union of these two uses is necessary for an organ 

 deserving the name of root; thus in certain plants, such 

 as the Fuci or the I^'y, we observe root-like appendages, 

 which fix them to solid bodies, but which do not serve 

 to absorb nourishment ; these are not roots, but Cramps 

 (crampons). In others, such as the Dodder, certain 

 peculiar tubercles absorb their nourishment, but do not 

 serve to fix them to the soil ; these are not roots, but 

 Suckers. Thus, every organ which unites the two 

 conditions above mentioned is a root, and all roots pre- 

 sent this double function, but with variations and modi- 

 fications, which deserve a detailed examination. 



The absorption of juices by the roots takes place solely 

 by the extremity of each radical fibril, or, which is to say 

 the same thing, by the spongioles which terminate each 

 of their ramifications. Duhamel had some idea of this 

 when he remarked that young trees exhaust the earth 

 very near their trunk, whilst old ones with horizontal 

 roots, such as the Elms on the sides of great roads, pro- 

 duce this exhaustion at a distance from their trmik, the 

 more considerable in proportion as they are larger. 

 Anatomists have confirmed this opinion, in remarking 

 the longitudinal direction of the fibres, and the thickness 



VOL. I. Q 



