52 



BULLETIN 380, U. S. DEPARTMENT OF AGRICULTURE. 



SOIL CONDITIONS. 



Greater opportunity for infection seems to be an important factor 

 in the greater abundance of Endothia in the South. By far the most 

 favorable places of infection, especially for EndotMa gyrosa, are 

 bruised or broken but still living roots. Soil, cultural, and climatic 

 conditions combine to make these many times more abundant in 

 the Southern States than elsewhere. The more sandy and easily 

 eroded soil, usually without turf, subject throughout the winter to 

 the action of wind and rain, leaves innumerable oak roots exposed, 

 which are readily injured by vehicles and the tramping of horses and 

 cattle, leaving wounds suitable for the entrance of Endothia. In the 



FIG. 4. Map of the United States, showing the distribution of Endothia, parasitica in 

 December, 1915. The solid portion shows the area in which E. parasitica is generally 

 present. The dots indicate scattered infections. The heavy line shows the limits of 

 the range of Castanca dcntata. 



North, the more rocky soil, frequently covered with sod, protected 

 through much of the winter by snow, makes exposed roots much less 

 common, and the roots so exposed are rather less subject to mechani- 

 cal injury. In the writer's experience the most favorable localities 

 for collecting E. gyrosa are the unfenced public squares of Southern 

 towns, where partial grading, erosion, and constant traffic have left 

 hundreds of oak roots exposed, and the pastures of southwestern In- 

 diana, where the roots of Fagus are often found injured by cattle. 



COMPETITION AMONG FUNGI. 



The writers' extensive field studies and observations have con- 

 vinced them that competition among fungi must be considered as a 



