J48 HOW CROPS GROW. 



veniently presented and discussed under a series of propo 

 sitions, viz.: 



1 Among the substances which have been described, 

 ( 1,) as the ingredients of the ash, the following are in 

 variably present in all agricultural plants, and in nearly 

 nil parts of them, viz/ 



( Potash 



Soda 

 Bases -j Lime Acide 



Magnesia 

 I Oxide of iron 



Chlorine 

 Sulphuric acid 

 Phosphoric acid 

 Silicic acid 



Carbonic acid 



2. Different normal specimens of the same kind 

 have a nearly constant composition. The use of il\ 

 nearly in the above statement implies what has* 

 ready intimated, viz., that some variation is noticec 

 relative proportions, as well as in the total quantity of 

 ash-ingredients occurring in plants. This point will 

 shortly be discussed in full. By taking the average of 

 many trustworthy ash-analyses, we arrive at a result 

 which does not differ very widely from the majority of the 

 individual analyses. This is especially true of the seeds 

 of plants, which attain nearly the same development under 

 all ordinary circumstances. It is less true of foliage and 

 roots, whose dimensions and character vary to a great ex 

 tent. In the following tables (p. 150-156) is stated the com 

 position of the ashes of a number of agricultural products, 

 which have been repeatedly subjected to analysis. In 

 most cases, instead of quoting all the individual analyses, 

 a series of averages is given. Of these, the first is the 

 mean of all the analyses on record or obtainable by the 

 writer,* while the subsequent ones represent either the re 

 sults obtained in the examination of a number of samples 

 by one analyst, or are the mean of several single anal- 



* The numerous ash-analyses, published by Dr. E. Emmons and Dr. J. II. 

 Salisbury, in the Natural History of New York, and in the Trans, of the N. Y. 

 S: i!r Aj. Society, have been disregarded on account of their manifest worthless- 

 IIO*D and absurdity. 



