THE ASH OF PLANTS. 149 
yses. In this way, it is believed, the real variations of 
composition are pretty truly exhibited, independently of 
the errors of analysis. 
The lowest and highest percentages are likewise given. 
These are doubtless in many cases exaggerated by errors 
of analysis, or by impurity of the material analyzed. 
Chlorine and sulphuric acid are for the most part too low, 
because they are liable to be dissipated in combustion, 
while silica is often too high, from the fact of sand and soil 
adhering to the plant. 
In two cases, single and perhaps incorrect analyses by 
Bichon, which give exceptionally large quantities of soda, 
are cited separately. 
A number of analyses that came to notice after making 
out the averages, are given as additional. 
The following table includes both the kernel and straw 
of Wheat, Rye, Barley, Oats, Maize, Rice, Buckwheat, 
Beans, and Peas; the tubers of Potatoes; the roots and 
tops of Sugar Beets, Field Beets, Carrots, Turnips, and 
various parts of the Cotton Plant. 
For the average composition of other plants and vege- 
table products, the reader is referred to a table in the ap- 
pendix, .p. 376, compiled by Prof. Wolff, of the Royal 
Agricultural Academy of Wurtemberg. That table in- 
cludes also the averages obtained by Prof. Wolff for most of 
the substances, cotton excepted, whose composition is rep- 
resented in the pages immediately following. Any dis- 
crepancies between Prof. Wolff’s and the author’s figures 
are for the most part due to the use of fewer analyses by 
the«former. 
In both tables, the carbonic acid, which occurs in most 
ashes, is excluded, from the fact that its quantity varies 
according to the temperature at which the ash is pre- 
pared. 
