DAMPING-OFF IN FOREST NURSERIES. 
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Fig. 9. — Diagram showing the progress of damping-off in treated plats 
(solid line) as compared with untreated plats (broken line). Graphs 
1 to 4 represent Pinns ponderosa ; graphs 5 to 8, P. resinosa; graph 9, 
P. banksiana; and graph 10, plats each of which was half P. nigra 
poiretiana and half P. sylvestris. Nurseries in Kansas, Nebraska, Minne- 
sota, and Michigan are represented. The relatively high total number 
damped-off in the treated plats shown in two of the graphs is due to the 
fact that a large proportion of the seedlings in the untreated plats had 
been killed before they appeared above the soil surface. In both the 
cases in which the absolute number of seedlings killed was as great 
in the treated plats as in the controls, the percentage of the seedlings 
killed was nevertheless lower and the survival more than twice as good 
as in the controls. 
19651°— Bull. 934—21 2 
