CHESTNUT BARK DISEASE. 441 
the spores the higher the percentage of infection. For instance, 
on chestnut seedlings, cultures varying from 28 to 55 days old 
gave successful inoculations varying from 100 to 50 per cent.; 
while those 79 to 250 days old gave from 39 to o per cent. 
However, with the latter the time of inoculation may have 
entered into the problem, since in no case did we try to inoculate 
on the same date with spores of greatly different ages. 
Time of Inoculation. Inoculations made in the spring are 
more successful than those made in midsummer, at least those 
we made in the spring were, as a rule, much more successful 
than those we made in July. However, as just stated, those 
made in the spring were made with younger spores than those 
made later, and just how much of the failure of the latter was 
due to the time of inoculation and how much to the age of the 
spores could not be determined. We have also tried inoculations 
on dormant seedlings in the greenhouse, and these have either 
failed to take or took only after the trees began to grow. The 
length of time the fungus has been in culture, age of the spores 
used, time of year the inoculation is made, are all points that 
need further investigation to bring out their bearings more 
clearly. 
Condition of Host. We tried several experiments to deter- 
mine what effect the condition of the host had on the success of 
the infection. These experiments included a few plants kept 
unusually wet and others very dry, in the greenhouse; others 
severely ridged outdoors to aid in drought conditions, com- 
pared with plants not ridged; and plants with knife cuts encir- 
cling the bark (in some cases with a band of bark removed) 
which were inoculated above and below these injured places. 
The results were rather conflicting, so that we could not tell 
whether or not these treatments made any special difference. 
Inasmuch as they did not show more striking evidence in favor 
of increased blight development under unfavorable ‘conditions 
of the host, perhaps they may be interpreted as rather against, 
than in favor of, our theory that the condition of the host 
affects the prominence of the fungus as a parasite. However, 
such experiments need to be made in greater number and during 
several seasons in order to judge accurately as to results. 
cS 
