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 Pinus ponderosa ; graphs 5 to 8, P. resinosa ; graph 9, 

 P. banksianaj 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 s-eedlings 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 



