76 NUTRITION. 



NUTRITION. 



29. All vegetable life in whatever form presented to 

 us, is essentially dependent for its continuance on the 

 process of nutrition, and this therefore must be consi- 

 dered as one of the fundamental objects of all living 

 plants, and the conditions necessary for the performance 

 of it as the most fundamental laws of their vitality. 



30. Absorption is the mode by which the entrance of 

 nutritious matter finds its way into the plant, and this 

 seems to take place in a simple though active manner, 

 no contraction of living solids accompanying the process. 



31. The root is the chief organ by which absorption 

 of such matter takes place, though no doubt can exist 

 that the leaves, &c., lend their aid, though to a less 

 degree. 



32. It has been supposed that at a particular portion 

 of the root (the spongiole or extremity of the radicle) 

 absorption alone takes place, and the experiments of 

 Senebier and others are adduced in support of it ; ne- 

 vertheless, it was known to De la Baisse before him, 

 that this is not alone the absorbing surface ; and from 

 later experiments we may conclude the surface of the 

 root generally absorbs, though the quantity and velocity 

 of the absorption may be comparatively small to that 

 seen taking place at the extremities of the radicles. 



33. Whatever nutritive material is absorbed by the 

 roots, it must be held in complete solution in water ; no 

 substances, either solid or mechanically mixed with it, 

 can find entrance into the plant. 



34. Some persons believe that roots will absorb colour- 

 ing matter along with the water in which they are grown ; 

 and Biot has said that he coloured the white flowers of 

 a Hyacynth, by making it absorb the juice of Phytol- 

 lacca dicandra ; this same experiment has been institu- 

 ted for more than one hundred years, according to ano- 

 ther writer, but the results obtained at different times 



