DAMPING-OFF IN FOREST NURSERIES. 
33 
had the high value of 63±9.7 per cent. The graph indicates also a 
decided, though less extreme, degree of variability for Peltier's 
strains on carnations ; the survivals for the 18 strains which he used 
in both of his experiments on cuttings have a variability coefficient 
of 29 ±3.5 per cent and the 23 strains in experiment 2 on seedlings 
55±6.9 per cent. 
R>YTH/UM DEBRRY/9A/UM 
• oo 
CORT/C/UM UYfGUM 
WR/TER& &TRR/MS ON R/A/E 
□ 
□ 
m 
□ 
□□ □ D 
cP 
□□□ 
nRElT/ERS STRrt/MS O/V C/9RN*T/ON CUTTtNGG 
□ □ □ 
DDDDnnn dd d dd d 
RELT/ER'S STRM/VS ON CRRHRTtOM SBEOUNGS 
d a 
DD D DDD DD 
DD DDDDDDD DDDD 
O 20 40 so eo /oo 
RIR/VTS &URI//WA/0 RER /OQ/M CONTROLS 
Fig. 13. — Diagram showing the results of inoculations with IT strains of Corticium vagum 
and 35 strains of Pythium dcbaryanum, arranged in decreasing order of virulence from 
left to right, as indicated by the survivals in pots of pine seedlings artificially inoculated 
. with them. The Pythium results represent the mean survivals in 5 pots inoculated with 
each strain in each of experiments Xos. 66, 67, and 68. Each point located is therefore 
based on the results in 15 pots, 10 of Pinus banksiana and 5 of P. resinosa. The 
Corticium results on pine represent 5 or 6 pots each, in two experiments (Xos. 71 and 72) 
on P. resinosa. The outline circles represent P. debaryanum strains from East Tawas, 
Mich. ; the solid circles represent strains from other localities. The second row of 
squares shows the sum of the results in Peltier's experiments Xos. 1 and la (99, his 
table 3). The lowest row of squares shows his results in experiment No. 2 (his 
table 4). 
• 
The strains represented in figure 13, as used on pine, include 1 
from bean, 2 from potato, 1 from sugar beet, 1 from Elaeagnus, 2 
from Picea engelmanni, and 10 from Pinus resinosa, P. ponderosa, 
and P. oanksiana. Two were, from Washington, D. C, 2 from Xew 
York, 1 from Ohio, 4 from Michigan, 4 from Minnesota, 1 from Ne- 
braska, 2 from Kansas, and 1 from California. The sources of these 
strains are widely distributed both as to host and locality : they are 
19651°— Bull. 934—21 3 
