318 



LEAVES AND ROOTS— THEIR FUNCTIONS AND STRUCTURE. 



combined action of moistxire, heat and oxy- 

 gen, itpo7i the germ, that the vitality of the 

 plant is excited. Moisture is absorbed, and 

 carbonic acid gas is generated, the pluviula 

 puts forth its tiny leaves, and the radicle 

 elongates and penetrates the earth. That 

 tke oxygen of the atmosphere is the prime 

 mover in this action, which, in this process, 

 is called germination, is abundantly testi- 

 fied by the fact, that seeds will not germi- 

 nate without its presence, and that the very 

 act of germination is accompanied with the 

 generation of carbonic acid gas. The mois- 

 ture supplied takes up that portion of the 

 starch which has undergone the chemical 

 change ; and a preparation of a seed in 

 this state, will show that the duct or vessel 

 into which the nourishment, so prepared, 

 enteTs, leads directly into the plumula or 

 evolving leaves of the young plant. Now, 

 a process somewhat similar takes place 

 with the root and rootlets of a plant. To 

 excite vegetation, moisture, heat, and oxy- 

 gen are required; and vegetation is ac- 

 companied with the same act of generating 

 carbonic acid gas. You will bear in mind 

 that the vessel, in the centre of the rootlet, 

 does not only run the whole length of the 

 rootlet, but penetrates transversely through 

 the bark, and joins the inner or ascending 

 sap vessels. It therefore appears that the 

 following process goes on: The concen- 

 trated juice, contained in the root, is in the 

 rootlet subjected to the influence and action 

 of the oxygen of the atmospheric air, and 

 water, contained in and permeating the 

 soil. A portion of the moisture is imbibed 

 through the coats of the vessels, and di- 

 lutes the juice contained in them ; and, 

 being forced through the internal coat, by 

 endosmose, into the internal or ascending 

 vessels, it meets and mixes with the water 

 taken up by the spongioles, holding in so- 

 lution the various alkaline and siliceous 



compounds necessary for the inorganic 

 structure of the plant. This mixture, con- 

 stituting the true sap, ascends by the force 

 of endosmose and capillary attraction, and is 

 thus capable of forming the new leaves, the 

 wood, the flowers, and the fruit of the plant. 



Let me explain, to those unacquainted 

 with the term, the meaning of endosmose. 

 It has been long known that no gas or par- 

 ticular air can be confined by animal tex- 

 ture ; and that if a bladder is filled with 

 any gas, it cannot be kept pure for any 

 length of time ; that which is within escapes 

 through the coats of the bladder, and that 

 which is without will get in, and vice 

 versa, according to fixed and known laws. 

 Now it has been found that fluids are pos- 

 sessed of similar powers, and governed by 

 similar laws, acting in this manner on 

 membrane of either animal or vegetable 

 structure, alike, — the lighter fluid forcing 

 itself through the integument, and mixing 

 with or passing that of greater density ; 

 and after water, a gummy solution ranks 

 first in endosmodic power. Now, as the 

 juice in the roots abounds in gum, it fol- 

 lows that water imbibed through the exter- 

 nal coat of the rootlet, and diluting the 

 proper juice intp their mucilage, the solu- 

 tion is forced by endosmose into the inner 

 vessel, and ascends by that force and capil- 

 lary attraction. It is on this principle we 

 account for the ascent of the sap, and on 

 no other, in my opinion, can the theory of 

 vegetation, the development of the plant, 

 and production of its woody fibre, be ex- 

 plained. 



Assuming, then, that all the carbon of 

 the plant is derived from the atmosphere, 

 and that a quantity of this constituent is 

 required, not only for the due evolving of 

 the leaves and wood, but for their subse- 

 quent nourishment, it follows that a certain 

 portion of this necessary ingredient must 



