148 HOW CROPS GROW. 



vcniently 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 

 all parts ofthem^ viz.: 



f Potash f Chlorine 



Soda Sulphuric acid 



Bases \ Lime Acids < Phosphoric acid 

 Magnesia Silicic acid 



[ Oxide of iron [_ Carbonic acid 



2. Different normal specimens of the same kind of plant 

 have a nearly constant composition. The use of the word 

 nearly in the above statement implies what has been al- 

 ready intimated, viz., that some variation is noticed in the 

 relative proportions, as well as in the total quantity, of 

 ash-ingredients occurring in plants. This point will 

 shortly be discusse'd 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. H. 

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

 State Ag. Society have been disregarded on account of their manifest worthless- 

 ness and absurdity. 



