Soda-Salts in Agriculture. 299 



from the soil, but also of retaining' this alkali and using it for 

 building up the living organs of the plant. 



Soda and its saline combinations unquestionably are also taken 

 up by plants from the soil and circulated throughout the vege- 

 table organism, but it is questionable whether soda, like potash, is 

 ever transformed in conjunction with carbon, hydrogen, nitrogen, 

 and other elements, into a living organ, in which the properties of 

 the alkali are no longer recognisable, but are as completely 

 changed as those of hydrogen, or carbon, or oxygen when enter- 

 ing into chemical combination with each other. 



It is true we find soda-salts, more especially common salt, 

 in almost every kind of agricultural produce, and their pre- 

 sence is commonly regarded as a proof that they are absolutely 

 necessary for the very life and growth of our cereal and forage 

 crops. The mere presence of certain constituents in plants does 

 not, however, prove that these constituents are indispensable. Such 

 a conclusion is only established when the withdrawal of one or more 

 elements of nutrition, or the substitution of others in their place, 

 is marked uniformly by an unhealthy growth and final failure. 

 Thus we know positively that no plant can grow healthily with- 

 out phosphoric acid or potash, since numerous attempts to find 

 a substitute for them have all been totally unsuccessful. Hence 

 our present state of knowledge entitles us to consider these two 

 substances to be essential ash-constituents of all plants. 



On the other hand, the fact that mangolds, or grass, contain 

 a good deal of common salt when the soil on which they are 

 grown is naturally rich in salt, or has received a good dressing of 

 it, does not by any means prove that salt is necessary ; or even 

 that it is, or may be, a useful manure for these crops. 



Like other soluble substances common salt and most other 

 soda-salts are readily absorbed by the rootlets of plants and con- 

 veyed into their sap, where they probably have important func- 

 tions to perform in the living plant. What these special functions 

 are we have yet to learn ; all we know is that salt is taken up 

 by plants, and under certain conditions which require yet to be 

 more clearly defined, has a remarkably good effect upon vegeta- 

 tion. Notwithstanding the large increase in the produce of 

 corn or roots which has in many cases been realised by the use 

 of salt, and its general presence in almost all plants, its base — the 

 soda — cannot be regarded as essential to the luxuriant growth 

 and maturity of plants. In many ash-analyses, made by our best 

 and most trustworthy analytical chemists, soda is not mentioned 

 at all, and merely traces of chloride of sodium are given. Ash- 

 analyses in which soda does not occur are not isolated or excep- 

 tional cases, but may be readily found on looking over a list of 

 such analyses endorsed by the names of Boussingault, Fresenius, 



