DAMPING-OFF IN FOREST NURSERIES. 
31 
probable error. Peltier's results permit similar correlations for the 
18 strains common to his experiments 1 and 1A on carnation cuttings 
and for the 22 strains common to experiment 1 on cuttings and ex- 
periment 2 on seedlings. The coefficients found are decidedly lower 
than those obtained from the experiments on pine, 0.51 ±0.117 for 
the experiments on cuttings and 0.36 ±0.121 for the comparison 
of the results on cuttings with the results on seedlings, but neverthe- 
less indicate some interexperimental correlation for the same strains 
and therefore inherent differences in parasitic ability between the dif- 
ferent strains. 
STRfi/NS OF COffT/C/UM l/f?GUM 
Fig. 11. — Diagram showing the comparative virulence of 29 strains of Corticium vagum 
in two successive inoculation experiments on Pinus resinosa. The results in experiment 
Xo. 71 are shown by the solid line, the strains being arranged from left to right in the 
order of descending virulence indicated by the number of seedlings surviving in this 
experiment. The results from the use of the same strains in experiment Xo. 72 are 
shown by the broken line. The obvious correlation between the two curves (coefficient 
0.81 + 0.04) indicates a real difference in virulence between the different strains. The 
strains indicated by the underscored numbers are original strains and those not under- 
scored reisolations from the original strains in earlier inoculation experiments on pine 
seedlings. 
In the work on pine seedlings, with the possible exception of 
strains 230 and 233, there was no evidence of attenuation in arti- 
ficial culture. Strains 117 and 213, isolated in 1910 and 1911, re- 
spectively, seemed as strongty parasitic in experiments 71 and 72 
(1917 and 1918^ as any of the five strains isolated in 1916 or the six 
strains isolated in 1915. 
Of the 20 strains above mentioned, three pairs were isolated under 
such conditions and showed such later agreement in performance as to 
indicate their individual identity. For the purposes of considera- 
tion in the following paragraph, the one of these probably duplicate 
strains which happens to have the higher number was eliminated from 
each pair. The survival figures in pots inoculated with the 17 strains 
