36 



portion of any plant, at an early period of its growth, 

 and thus to economize its vital energies, rather than to 

 suffer them to be expended, and the supply to become 

 exhausted through a superfluous developement, and then 

 to deprive it of those very organs, by the action of which, 

 the expenditure would be again recompensed to the vital 

 energies. 



CHAP. V. 



ON THE NATURE, AND COMPOSITION OF 

 THE SOIL. 



Plants absorb fluids through the extremities or spon- 

 gioles of the roots, and it is thus that those portions of the 

 substances which serve them as their food, and are de- 

 rived from the soil, are carried into their system, in a 

 state of solution : these spongioles are not strictly to be 

 regarded as analogous to the mouths of animals, for they 

 are not provided with openings, and cannot imbibe even 

 the most impalpable powders ; their action seems to be 

 more analagous to that of the lacteals in animals, for 

 these, as well as spongioles, serve to convey fluids only. 

 These considerations render it necessary, that in the 

 composition of soil for the growth of plants, the follow- 

 ing important points shonld be held in consideration; 

 it should contain a sufficient ratio of organizable matter, 

 that is of substances which can be rendered available as 

 food to the plants ; it should readily absorb fluids, since 

 it is only when in a state of solution, that food can enter 

 into the structure of the plants; it should be sufficiently 

 retentive to avoid the risk of injury by reason of the 



