APR 1 1 1910 
The Ohio >\aturalist, 
PUBLISHED BY 
The Biological Club of the Ohio Slate University. 
LIBHA1 
NEW YC 
BOTANIC 
GARDE 
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 14& 
Hike— A Comparative Study of Four Genera of Horseflies 149 1 
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 number 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. a 
137 
