igo 7] Garden, Field, and Forest of the Nation. 61 
about us in that they have no chlorophyl — the material 
which gives the green color to the plants. 
In a Kansas soil it was found that there were as many as 
one billion, six hundred and eighteen million, six hundred and 
eighty-one thousand, eight hundred and ten bacteria in a 
single gram or small thimbleful from a field under examina- 
tion, while another field nearby had only a few over a 
million. As air is necessary for their existence, they rapidly 
decline in numbers as you go .down in the soil to a point 
where none is ever found. 
Many different families of these bacteria live in the earth, 
making their homes in the soil. They help to decompose it, 
thus transforming it into food. They draw vast stores of 
food supplies from the air. At every point they act as 
agents in advancing the interest of man. 
Four-fifths of the air we breathe is one of the most valuable 
plant foods, nitrogen. Some of this nitrogen is available in 
one form and some in another, but it must all be put into 
| such form that it may pass into the system of the plant and 
; be utilized in the building up of stalk and leaf and ripened 
I seed. 
I In portions of North Carolina I have seen a field worn out 
i by injudicious cropping, the plants struggling to grow in a 
depleted soil into what would be at best but a lean and 
starved maturity. In an immediatly adjoining field, with a 
0 soil of precisely the same character, with no advantage in 
point of moisture, heat, or sunshine, with precisely the same 
kind of seed planted as in the ’first case, were tall, strong, 
and thrifty plants, neighbors to the thin, yellow, beggarly 
1 ones of the first field. 
The only difference between the two was that when the 
seed were planted there was sprinkled in the rows of one 
field some plain simple dirt brought from another State, and 
the field that had this dirt sprinkled in its rows was the field 
with the strong and vigorous plants. What wrought the 
wonderful change was a colony of nitrifying bacteria, living, 
