314 
Journal of Agricultural Research 
Vol. I, No. 4 
MYCOlvOGICAL, AND PATHOEOGICAE STUDIES 
Isolation of the Fungus 
Examination of a wide range of material during the last three years 
has invariably shown the same type of fungous growth and spore for¬ 
mation, while no other fungi have been found, except in the later stages 
of the disease. It was considered very probable that the fungus above 
mentioned was the cause of the diseased condition which it accompanied, 
and so on October 4,1911, single spore cultures were started, using conidia 
from material collected August 29, i9ii,at Baconton, Ga. Synthetic 
agar was used, and the germination was followed under the microscope 
from day to day. Growth was rather slow at first, but continued until 
at the end of a month colonies 5 to 15 mm. in diameter had been formed. 
Prom one of the strains obtained in 
this way the first inoculation tests 
were made. 
Inoculations 
The inoculation work was carried 
out during the winter and spring 
of 1912 upon young seedling pecan 
trees in the greenhouse. The leaves 
to be used in the tests were mois¬ 
tened with water immediately pre¬ 
ceding inoculation, and since no 
definite spore formation has taken 
place in culture, bits of the mycelial growth were placed directly on the 
upper or lower sides of the leaves thus moistened. The small potted trees 
were then generally left for several days under bell jars, with slight ven¬ 
tilation at the base, to insure proper humidity for growth of the fungus. 
Check trees in each experiment were treated similarly, with the excep¬ 
tion of the inoculation. 
Fig. 3.—Cross section of a leaf infected with the 
brown leaf-spot fungus from pure culture. X 250. 
Experiment No. i (Feb. 29, 1912). —The young leaves of two potted seedlings 
were inoculated from 3-weeks-old oxalic-acid and synthetic-agar cultures (strain 
33), the first tree being covered with a bell jar and the second left open. Two 
check trees were placed under a bell jar. The inoculated and check trees were 
all sprinkled with tap water on the second and fifth days and the bell jars were removed 
on the latter date. At the end of two weeks most of the inoculated leaves on the first 
tree had developed small, reddish brown areas from mere angular flecks up to irregu¬ 
larly circular spots 1 mm. in diameter. Very little infection had occurred on the tree 
left uncovered after inoculation, but several distinct spots were noted. Eater, many 
of the spots had increased in size up to 7 or 8 mm., with the development of tawny 
clusters of conidia visible to the naked eye upon the upper leaf surface. In no case 
did the check trees show signs of the disease. 
Experiment No. 2 (Apr. 16, 1912). —In a similar manner the tender leaves of a 
seedling were inoculated on both surfaces from a month-old com-meal-agar culture 
(strain 33). This tree and the check were left under a bell jar for five days. Observa¬ 
tion after a month showed a large number of the somewhat angular young spots up 
