148 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 
all parts of them, viz.: 
Potash - (Chlorine 
Soda Sulphuric acid 
Bases 4 Lime Acids 4 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 discussed in full. By taking the average of 
many trustworthy ash-analyses, we arrive at a result 
which does not differ very widely trom 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. 
