I'he Ohio T^aturalist, 



PUBLISHED BY 



The Biological Club of the Ohio State Uni'versity, 

 Volume X. APRIL. 1910. No. 6. 



TABLE OF CONTENTS. 



Dachnowski — The Bacterial Flora as a Factor in the Unproduct veness of Soils 137 



Fox— The Film Test for Crude Rubber 146 



HiNE— A Comparative Study of Four Genera of Horseflies 149 



Dickey— Meetings of the Biological Club 152 



THE BACTERIAL FLORA AS A FACTOR IN THE UNPRO- 

 DUCTIVENESS OF SOILS.* 



Alfred Dachnowski. 



The splendid contributions concerning the general relation- 

 ship existing between soil micro-organisms and scientific agri- 

 culture are their own testimony as to the soundness of this 

 position. Of these contributions the subject of nitrification is 

 one which has received the larger share of attention from scien- 

 tific men, and the literature thereon is indeed voluminous. The 

 value of nitrogen fixation by bacteria living within the soil itself 

 and by bacteria which develop nodules upon the roots of legu- 

 minous plants^ and the consequent increase in fertility of aban- 

 doned fields is a fact with which every student of agriculture has 

 become familiar. A role obviously less generally understood or 

 appreciated is that of micro-organisms in rendering a field or a 

 habitat injurious to agricultural crops. Micro-organic life in 

 soils and the relationship of such species as friends or foes to the 

 crop-producing capacity of soils is a line of research still before 

 us. It is one which offers splendid opportunities for the collec- 

 tion of facts of great moment to the practice of agriculture, 

 particularly in relation to the much debated question of fer- 

 tilizers. It will enable a better economic utilization and 

 conservation of soil resources. 



The ntimber of species concerned is exceedingly great. Some 

 are aerobic, while others are anaerobic. There are present not 

 only beneficial nitrifying bacteria upon which the formation of 

 important, valuable chemical compounds in the soil depends, 

 but also denitrifying, putrefactive, and pathogenic bacteria to 



*Contribution from the Botanical Laboratory of Ohio State Uni- 

 versity, 53. 



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ujILIBRARYI 



