FOREST DISEASE 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 suflicient 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- 
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Fic. 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 
