246 
Journal of Agricultural Research 
Vol. XXI, No. 4 
Only those subjected to 16 0 , 18.5°, and 21 0 C. for the 3 days after 
inoculation developed any scab on their leaves after removal to the 
greenhouse benches. 
On plants inoculated at 16 0 C. scab was just visible in 6 days from the 
time of inoculation, or 3 days from the time of removal from the temper¬ 
ature chamber. In 2 weeks the scab lesions were well marked. 
Plants inoculated at 18.5 0 C. showed a slight indication of scab 5 days 
after inoculation, or 2 days after plants were removed from the temper¬ 
ature chamber. In this case the scab lesions were well marked in 11 days 
from time of inoculation. 
Plants inoculated at 21 0 C. showed a slight indication of scab 5 days 
after inoculation, as was true of those at 18.5°. In 7 days the diseased 
spots were quite distinct, and in 11 days they had developed into definite 
and typical scabs. On plants inoculated at 13.5 0 , 24.5°, 27.5 0 , and 32 0 , 
however, no sign of lesions developed. 
Control plants were also kept under the same conditions, but none 
of these developed scab lesions at any time. The two plants which were 
inoculated with the fungus at the time the others were taken out of the 
temperature chambers and from whose surfaces the water was allowed at 
once to evaporate also remained free from scab. These were considered 
to be additional controls. The nonappearance of scab on these two plants 
indicated that infection at exposures of 16 0 , 18.5°, and 21 0 C. developed 
because the hyphae had penetrated while the plants were still in the 
temperature chambers. This conclusion is also supported by the fact 
that the time from inoculation to the appearance of visible scabs agrees 
well with that observed in previously reported tests (2, 3). The time 
elapsing between the removal of the plants to the greenhouse bench and 
the first appearance of scab appears generally to be too short to represent 
the incubation period of the fungus within the tissues of the host. 
On September 28, 1917, a set of young pomelo seedlings with leaves 
just begining to unfold was inoculated in the same manner as that 
described for the sour-orange seedlings of the third test, except that these 
were left four days in the temperature chambers instead of three. With 
the exception of one leaf on a plant inoculated at 18.5 0 C., which developed 
a slight indication of disease but no distinct scab, there was no visible 
sign of disease on any of the plants up to October 17, when the last 
observation was recorded. 
In all four tests just considered, scabs were always confined to rapidly 
growing leaves. The older leaves always remained free from the disease 
in every test. Neither was there any development of scabs on any of the 
large number of similar plants kept in the greenhouse and not inoculated. 
