May 16,1931 
Temperature Relations of Cladosporium citri 
245 
allowed to dry. The plants that had been inoculated at i6°, 19 0 , and 23 0 
subsequently became diseased. The plant from the 16 0 chamber had 
scabs just visible 7 days from date of inoculation. Those from the 19 0 
and 23 0 chambers were not seen to be diseased until 10 days later. The 
plants that had been inoculated at 16 0 and 19 0 had many scabs. The 
plant that had been inoculated at 23 0 was only slightly diseased even on 
the seventeenth day after inoculation. 
Controls which were not inoculated, but on which distilled water was 
drawn over the leaves, were subjected to 16 0 and 26.5° C. and kept under 
the same conditions as the others,, but no scab developed upon them. 
A second test on sour-orange seedlings just like the first was made on 
June 5, 1917, except that different temperatures were maintained in 
some of the chambers and two plants were left in each temperature, and 
they remained for 54 hours instead of 3 days. Control plants not inocu¬ 
lated were used at 20° and 27.5 0 C. The average temperatures in this 
test were 14 0 , 20°, 24.5 0 , 27.5 0 , 32.5 0 , 36°, 40°, and 44.5 0 . 
In this test one of the plants inoculated at 20° C. developed scabs on its 
leaves. These were first noted two weeks after inoculation. None of the 
other plants developed scabs. As will be seen in Table I, the chamber at 
20 0 is the only one that lies in the range at which infection occurred in the 
other two tests, namely, 16 0 to 23 0 . The chambers at 14 0 and 24.5 0 , 
therefore, appeared to be outside, one below and the other above, the 
range for infection. 
On September 24, 1917, a third inoculation test was made with sour- 
orange trees in pots, about one year from seed, on which small new leaves 
were developing. The plants were surrounded by cylinders of blotting 
paper kept moist by absorption of water from below. Another piece of 
blotting paper was placed over the top of the cylinder. The different 
temperature chambers (7) in which the plants were left for 3 days 
were maintained nearly constant within a fluctuation of about 0.5 0 C. 
At the end of this 3-day period when they were taken out, the moist 
cylinders of blotting paper were removed, and the plants were set in the 
greenhouse. In about yi hour the moisture had evaporated from the 
surfaces of the plants. At the same time that these were taken out, two 
other plants were inoculated with the fungus as before and were set in the 
same greenhouse and under the same conditions as the others. These 
were not surrounded by blotting paper but were allowed to dry like the 
others, after water with spores had been drawn over their leaves. 
The temperatures at which the plants remained during the 3-day 
period in the saturated atmosphere of the dark chambers were 13.5 0 , 16 0 , 
18.5°, 21 0 , 24.5 0 , 27.5 0 , and 32 0 C., respectively. 
The temperatures recorded in the greenhouse for the 12 days after the 
plants were taken out of the temperature chambers gave an average 
minimum of 15 0 C., and an average maximum of 30°. 
