46 TERRESTRIAL ADAPTATIONS. 



time. In like manner, a diminution of the 

 gravity of the vegetable juices would accelerate 

 the rising of the sap, and would, probably, hurry 

 and overload the leaves and other organs, so as 

 to interfere with their due operation. Some in- 

 jurious change, at least, would take place. 



Here, then, we have the forces of the minutest 

 parts of vegetables adjusted to the magnitude of 

 the whole mass of the earth on which they exist. 

 There is no apparent connection between the 

 quantity of matter of the earth, and the force of 

 imbibition of the roots of a vine, or the force of 

 propulsion of the vessels of its branches. Yet, 

 these things have such a proportion as the well- 

 being of the vine requires. How is this to be 

 accounted for, but by supposing that the circum- 

 stances under which the vine was to grow, were 

 attended to in devising its structure ? 



We have not here pretended to decide whether 

 this force of propulsion of vegetables is mechani- 

 cal or not, because the argument is the same for 

 our purpose on either supposition. Some very 

 curious experiments have recently been made, 

 (by M. Dutrochet) which are supposed to show 

 that the force is mechanical ; that when two dif- 

 ferent fluids are separated by a thin membrane, 

 a force which M. Dutrochet calls endosmose urges 

 one fluid through the membrane : and that the 

 roots of plants are provided with small vesicles 

 which act the part of such a membrane. M. 



