138 ON THE FOOD OF PLANTS. 



others, and that they sometimes, like some 

 animals, feed on gross impurities j is distinctly 

 proved by the flavor of esculents, and parti- 

 cularly the cabbage tribe : thus we find that 

 sea-kale, growing in rank manured beds, is so 

 gross and bitter in flavour, as scarcely to be 

 eatable; whilst that which is grown in a pure 

 natural soil, is sweet and delicious. 



Certainly, we cannot pretend to the powers of 

 determining and measuring out the exact pro- 

 portions of the required elements ; but we may, 

 by a little attention, be able to counteract and 

 avoid extremes. 



It appears throughout nature, that the efforts 

 of a plant, from its first establishment, is directed 

 to acquire the proper state and condition to 

 propagate its species ; and that in its seeds and 

 fruit is comprised its concentrated essence. We 

 may therefore estimate its powers and efforts to be 

 in proportion to its wants ; and hence we may sup- 

 pose, that as starch, and sugar, contain a large 

 portion of oxygene, and a small portion of hy- 

 drogene; that those plants whose desired pro- 

 ducts consist of such substances, should be sup- 

 plied with food containing a large portion of 

 carbon and oxygene ; and as oil contains a large 

 proportion of hydrogene, and no oxygene ; that 

 to those vegetables, whose seeds produce oil, a 



