Chapter IX

SOIL AND SUBSOIL (_continued_), 142.—ORGANISMS INFLUENCING
SOIL-CONDITIONS. BACTERIA, 142.—_Micro-organisms of the
Soil._ Bacteria, Moulds, Ferments, 142.—Numbers at Various
Depths, given by Early Observers, 142.—Investigations of
Hohl; Mayo and Kinsley. Tables, 143.—Multiplication of the
Bacteria, 144.—Aerobic and Anaerobic Bacteria, 144.—Food
Materials required, 145.—Functions of the Bacteria,
145.—Nitrifying Bacteria. Figures, 146.—Conditions of
their Activity. Table, 146.—Effects of Aeration and
Reduction, 147.—Unhumified Organic Matter does not Nitrify,
148.—Unhumified Vegetable Matter, Functions in Soils,
148.—Denitrifying Bacteria. Figures, 148.—Ammonia-forming
Bacteria. Figures, 149.—Alinit, 149.—Effects of Bacterial
Life on Physical Soil Conditions, 149.—Root-bacteria, or
Rhizobia of Legumes, 150.—Figures of Root Excrescences
and Corresponding Bacteroids, 152.—Varieties of Forms,
154.—Mode of Infection, 154.—Cultural Results, 155.—Table
Showing Increased Production by Soil Inoculation,
155.—Other Nitrogen-absorbing Bacteria, 156.—Distribution
of Humus in the Surface Soil, 157.—Fungi, Moulds and Algae,
157.—_Animal Agencies_—Earthworms, Insects, Burrowing
Quadrupeds, 158.