DAMPING-OKI-' IX KOIIKST N TUSKKIKS. 31 



probable error. Peltier's results permit similar correlations for the 

 18 strains common to his experiments 1 and 1A on carnation cuttings 

 ami 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 0.124 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. 



r 



Fiii. 11. Diagram showing the comparative virulence of 29 strains of Corticium vayum 

 in two successive inoculation experiments on Pinus resinosa. The results in experiment 

 No. 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 No. 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 147 and 213, isolated in 1910 and 1911, re- 

 spectivel} 7 . seemed as strongly 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 



