636 The Philippine Journal of Science 1920 
raised margin forms around the outer edge while the center some- 
times becomes depressed, and assumes a light tan or brownish 
color. Pycnidia sometimes show in the depressed, lighter-colored 
area; they are black, and a mere fraction of a millimeter 
in diameter. The lesion not only occurs on the surface but ex- 
tends into the skin tissue for 1 or as much as 2 millimeters. In 
this internal tissue the lesion is usually lighter colored—the 
reddish brown of a young lesion. The lesion has never been 
observed to extend into the flesh of the fruit, although rarely 
secondary rots, emanating from a black-spot lesion as the origina] 
point of infection, may progress into the flesh. The colored 
photograph, Plate 1, shows the disease much better than a written 
description can do. 
The disease is not abundant on fruits in the orchard, but seems 
to develop while they are in storage, or in transit to markets. 
We have shipped fruits entirely unblemished, which on unpacking 
one month later were found severely affected by this black spot. 
The injury to the crop is much the same as that of citrus canker 
on fruits, and is due to a blemish which lessens its selling value. 
In a very few cases, the black-spot lesions afford an entrance 
for rot fungi, but such cases are rare. 
DISTRIBUTION 
This disease has been observed at Canton, Hongkong, Swatow, 
Amoy, and Foochow in China. Specimens which emanated from 
Shanghai have been intercepted by the plant-quarantine inspec- 
tors at Nagasaki. Chinese fruits have been collected on the mar- 
kets in Manila, which were severely affected by this disease, but 
Philippine-grown fruits have not been observed as yet to be 
affected. McAlpine, of course, originally reported the disease 
from New South Wales. The disease has not yet been observed 
in Japan nor has it been reported from California, Arizona, Flo- 
rida, or the Gulf States. The distribution on the China coast as 
far north as Foochow would indicate that the development of the 
fungus is not limited by the lower temperatures of citrus-grow- 
ing regions. That is to say, black spot of citrus fruits would 
seem to be a temperate zone disease. 
ISOLATION AND INOCULATION EXPERIMENTS 
Isolation experiments were first attempted in Nagasaki, and 
a fungus was obtained uniformly from such isolations. Sub- 
