Soil Changes Produced By Micro-organisms. 9 
green condition in the spring, the benefit from this is not apparent 
for three or four weeks. In other words, the plant food contained 
in the fresh stable manure or the green crop is locked up in some 
unavailable form which is of no use to growing plants until decom¬ 
position has set in. So far as the chemical elements present are 
concerned, they are essentially the same in both old and new 
manure, but the combinations are quite different after decay begins. 
Plants and animals, as well as the excrement from the latter, are 
made up of very complex compounds. Experience has taught us 
that it would be folly to attempt to grow a crop of oats on a barn 
floor by supplying the seed with fresh fish, alfalfa hay, or cotton¬ 
seed meal; but sow the oats in the ground, and let any of the above 
substances be incorporated with the soil, and in a reasonable length 
of time the effect of the fertilizer will be apparent. It would be 
equally absurd to think of raising a child, or a colt, or a calf, on a 
simple plant ration of nitrate of soda, superphosphate of lime and 
sulphate of potash with a little lime, magnesium, iron and sulphur 
for seasoning. Plants must have their food in a very simple form, 
while animals require theirs in a much more complex condition. 
Herein lies the explanation of the availability of plant food in 
thoroughly decomposed manures. 
Were it not for microorganisms, there could be no such thing 
as decomposition, and every dead plant and animal would remain 
forever unchanged upon the earth. Not only would this globe 
soon become a rather unsightly dwelling place, but the energy locked 
up in these inert bodies would be an extravagant waste. Nature 
has provided wisely for this exigency, and has stocked the air, 
soil, and water with myriads of microscopic scavengers. (Plate 
III, 3, 4, 5, 6.) Although these are tiny plants, they can obtain 
their food from the dead bodies of plants and animals. In their 
ability to break these down and simplify them so. that they can 
be of use to other plants, they rival our chemists with all of their 
splendid laboratory equipment. 
THE TRANSFORMATION OF CARBON. 
The chemical element, carbon, occurs in its purest form as the 
diamond and as graphite. We know it in a less pure state as coal, 
charcoal, coke and lamp black. When it is combined with hydro¬ 
gen, it forms such compounds as illuminating gas, acetylene, and 
marsh gas. In the plant world it is found associated with oxygen 
and hydrogen in the form of sugar, starches, cellulose, woody tis¬ 
sue, fats, and waxes, and when nitrogen and sulphur are added to 
these three elements, the resulting compound contains the essentials 
