94 DOES THE ACTION OF A SUBSTANCE DEPEND 



organic or mineral, in any state of chemical combination, if 

 equally soluble, be equally acceptable to a given plant, and 

 equally promote its growth ? So far as our knowledge goes, 

 it inclines us to answer no. Of two equally soluble states of 

 chemical combination of the same acid or base, the one may 

 produce, all other circumstances being the same, a more sensible 

 effect than the other. Whether this difference is to be ascribed 

 to the special influence of the second substance with which the 

 acid or base is combined, or to the special properties of the 

 compound body as a compound, are interesting theoretical points 

 which, by repeated field experiments, we are anxious to deter- 

 mine. 



But suppose these questions settled, another equally interest- 

 ing follows. If a plant A is most grateful for a substance in a 

 given form of combination, will another plant B be also most 

 grateful for it in the same form ? Will wheat and oats be equally 

 benefited by ammonia, or sulphuric acid, or phosphoric acid, or 

 lime, in the same state of chemical combination ? Will the bean 

 and the turnip prefer also to have them in the same form as the 

 kinds of grain we have mentioned ? These are interesting but 

 very deep questions, which only long and careful experimenting 

 can solve. 



But inasmuch as every plant contains and produces some 

 forms of matter (chemical combinations) peculiar to itself, it is 

 not unlikely that certain combinations of a given substance, 

 special for each plant for each variety, species, or genus may 

 favour its growth more than others will do. Can we even hope 

 to arrive at such refined knowledge as this ? But if we ever do, 

 how rich in direct practical applications will it be to the art of 

 tending and feeding our crops, of doctoring and economically 

 manuring our soils ? 



Sulphur exists in one peculiar state in our onion and garlic 

 crops, in another in our corn and common root-crops. The 

 potato and the parsnip produce starch, the carrot and the turnip 

 pectic acid; wheat produces gluten, the pea and the bean 

 legumin, and Indian com and the oat substances differing 

 from both. Are certain chemical forms of any given saline food 

 better adapted than other forms to the production of these 



