FOREST DISKASE SURVEYS. 



19 



of the various infections and to show therein the estimated cull due 

 to each. This information can easily be secured by coobservation 

 with the estimator, who can supply the actual figures for the rot 

 percentages and aid in determining the boundary lines of infec- 

 tion. This will produce sufficient reliable data upon which to base 

 valuable pathological maps, which can be compiled either with col- 

 ored areas to indicate the diseases and inclosed figures indicating the 

 rot percentages or can be drawn in black and white, using lines dif- 



Fig. 19. — Razoumofskya campylopoda, mistletoe, on yellow pine. 



fering from type lines to indicate the boundaries of the infected 

 areas and placing the rot percentages in figures within this area. 



PATHOLOGICAL MAPS. 



Maps indicating the distribution of diseases in forest areas have 

 not been used to any great extent. In German literature, articles 

 are to be found dealing with plant diseases which have such maps 

 illustrating the distribution of the disease. Very few contain maps 

 dealing with the distribution of forest-tree diseases and none at 

 all dealing strictly with the distribution of fungous infection in 

 forests. 



In this country considerable use has been made of disease-distribu- 

 tion maps by the various workers along the line of plant and forest 



