DAMPING-OFF IN FOREST NURSERIES. 
63 
than half as rapid. Chlamydospores are mostly intercalary, at first 
subspherical, soon becoming polygonal, and after a few days they 
shrivel and exhibit thick, angular walls. In size the unshrunken 
spores usually lie between 8 and 12 pi in diameter, but bodies as 
large as 20 \l occasionally occur. Antheridia have not been observed, 
and the shriveled bodies are not believed to be oospores, though the 
observations made have not been sufficient to exclude such a possi- 
bility. No other spore form was obtained in water culture, using 
various nutrient substrata. In inoculation the strain from. olive (the 
"undetermined Phycomycete" included in Table VIII) has given 
negative or nearly negative results in three inoculation tests in which 
other fungi gave positive results. In a test not included in the table, 
in which Pinus ponderosa was the trial host, damping-off was slightly 
higher in the inoculated pots than in the controls, but the difference 
was apparently due to accidental infection with Botrytis and 
Pythium debaryanum. As all the seedlings in pots inoculated with 
P. debaryanum in this additional experiment were killed, the rela- 
tive unimportance of this strain of the small-spored fungus was 
further indicated. An additional test of both the olive strain and 
the strain from soil was made by inoculating seedlings of Pinus 
banksiana and P. ponderosa growing on filter paper in Petri dishes. 
Some of these were kept wet with water, some with an inorganic- 
culture solution, and some with the inorganic solution plus peptone 
and dextrose. Agar cultures were applied directly to the seedlings. 
The seedlings inoculated with the small-spored fungus remained 
alive as long as the control seedlings, while parallel inoculations with 
Pythium debaryanum resulted in the early decay of the seedlings. 
Table VIII. — Results of inoculations with miscellaneous oomycetes on pines in 
autoclaved soil at the time of sowing. 
[In all the experiments included in this table, the inoculum consisted of fragments of agar cultures 
distributed with the seed at one side of each pot over about one-fourth of the pot area. The controls 
received sterile agar in the same way..] 
Num- 
ber of 
pots. 
Results. 
Experiment number, host, and inoculating fungus. 
Emerged. 
Damp- 
ing-off. 
Survival. 
No. 66, Pinus banksiana: 
Phytophthora sp.— 
Strain 358 
5 
5 
5 
4 
5 
25 
5 
5 
5 
5 
5 
23 
Per 5-pot 
unit. 
70 
75 
94 
115 
83 
75 
96 
88 
99 
102 
98 
87 
Percent. 
30 
28 
16 
14 
9 
14 
1 
3 

2 

5 
Per 5-pot 
unit. 
49 
Strain 372 
54 
Strain 375 
79 
99 
76 
64 
No. 67, Pinus banksiana: 
Phytophthora sp.— 
Strain 358.. 
95 
Strain 372.. 
. 85 
Strain 375.. 
99 
100 
98 
Controls 
83 
