CONTENTS XX1U 



denitrifying bacteria. Thermophilic bacteria. Pectin decomposing bac- 

 teria. Bacteria decomposing hydrocarbons and benzene ring compounds. . 190 



Chapter IX 



BACTERIA DECOMPOSING UREA, URIC, AND HIPPURIC ACIDS 



Organisms decomposing urea. Methods of isolation. Occurrence of urea 

 bacteria. Classification and description. Bacteria decomposing calcium 

 cyanamide. Uric and hippuric acid bacteria 206 



Chapter X 



SOIL ALGAE 



Introductory. Methods of isolation of impure cultures of algae. Isolation 

 of pure cultures. Cultivation of soil algae. Distribution of algae in the 

 soil. Occurrence of algae in the soil. Biochemical activities of algae. 

 Role of algae in the soil 215 



Chapter XI 



SOIL FUNGI 



Occurrence of fungi in the soil. Methods of demonstrating the occurrence 

 and abundance of fungi in the soil. Methods of cultivation of soil fungi. 

 Isolation of single spore cultures. Classification of fungi with special refer- 

 ence to those occurring in the soil. Occurrence of specific fungi in the soil. 

 Activities of fungi in the soil. Influence of reaction upon the growth of 

 fungi. Cellulose decomposition by fungi. Decomposition of nitrogenous 

 substances (ammonia formation). Utilization of nitrogen compounds by 

 fungi. Nitrogen fixation. Mycorrhiza Fungi. Nature of mycorrhiza 

 formation. Plants forming mycorrhiza. Organisms responsible for 

 mycorrhiza formation. Role of mycorrhiza in the nutrition of plants. . . . 236 



Chapter XII 



SOIL ACTINOMYCES 



General considerations. General description of the genus Actinomyces. 

 Terminology and systematic position. Species differentiation. Methods 

 of study. Nature of growth on artificial media. Vegetative mycelium. 

 Spore bearing mycelium. Utilization of carbon compounds by actinomyces 

 as sources of energy. Nitrogen utilization. Oxygen requirement. Influ- 

 ence of temperature, drying and radiation. Influence of reaction and salt 

 concentration. Influence of poisons. Reduction of nitrates and other 

 compounds. Production of odor. Pigment formation. Variability. 

 Species differentiation. Key to the identification of species of soil 

 actinomyces. Importance of actinomyces in the soil , , , 285 



