es, there are two elements that come largely from the atmosphere,
namely carbon and hydrogen, which, united with oxygen, make up the bulk
of the plant. Thus, wood is a substance containing carbon, hydrogen, and
oxygen, with small quantities of nitrogen and mineral salts. The mineral
salts represent about one per cent. of air-dried wood.

Having considered in a general way the constituents of the plant, and
having noticed the source of each of these constituents, it may be of
interest to look at the composition of the soil as revealed by chemical
analysis. "A" is the analysis of a soil from Finney county, as made in
the laboratory of the Kansas State University, by the author. "B" is a
soil from Wyandotte county, as reported in the report of the Kansas
State Board of Agriculture for 1874. "C" is a prairie soil from Dakota,
as reported by Prof. E. Richards, of the department of agriculture.

"A" "B" "C"
Silica and insoluble 71.66 82.16 69.82
Iron and aluminum oxides 6.55 6.70 12.05
Calcium oxide 4.41 .68 .85
Magnesium oxide 1.02 .06 .87
Phosphoric anhydride .18 .08 .11
Chlorine .01 .03 .03
Potassium oxide .75 .05 .72
Sodium oxide .25 .11 .94
Sulphuric anhydride .06 .39 .12
Volatile and organic matter 3.98 5.44 8.90
Moisture 9.67 3.80 6.27
Undetermined, carbonic acid, etc. 1.48 .30 .22
------ ------ ------
100.00 100.00 100.00

In some cases it happens that there is a sufficient quantity of an
ingredient in the soil, but it is not in a sufficiently _soluble_ form
to be available. It will be noticed that in the analyses quoted above
the amount of the necessary constituents of the soil to plant growth is
not in any case large. The nitrogen may be present in the volatile and
organic matter, and upon the proportion of this complex organic matter
very often depends to a great extent the fertility of the soil.

Some experiments made at one of the