RUBBER (HEVEA) DISEASES 47 
upper side. The disease does not appear to make further progress 
after this stage. The leaf remains attached for some time but falls 
prematurely. The diseased tissues contain hyphse. but the fruiting 
fungus was not found. 
Peteh has recorded three rim-blights in Ceylon, each being re- 
ferred to a different organism. In no case were they reported to 
cause serious damage. 
INDETERMINATE LEAF-SPOTS 
It has not been possible to determine with any degree of satis- 
faction the causal organism of a number of common leaf-spots 
found on Hevea. It is doubtful whether all of these pathological 
appearances are to be attributed to parasitic fungi. Usually two 
or more fungi may occur in association with the spots, and these 
may be merely saprophytic on the dead tissues. Not until it is pos- 
sible thoroughly to investigate the fungi experimentally in the field, 
in cultures, and by inoculations will the subject be elucidated. Some 
of these spots from their frequent occurrence and evident ability to 
destroy the leaves are of considerable economic importance. Others 
appear mainly at about the time of normal leaf fall and probably 
somewhat hasten the process. One such spot was frequently found 
on leaves under heavy canopy. Small yellowish translucent spots 
from 1 to 5 millimeters in diameter appear as a first stage. In the 
center of the yellowish areas dark reddish brown spots appear, and 
the leaf assumes a light-purple color. When the leaf is held to the 
light the spots are very conspicuous. The purple color of the leaf 
deepens to reddish purple, the yellow border may appear greeni.-h. 
and the central spot becomes black, with the development of a white 
superficial mycelium. A peculiar effect accompanying this disease 
is the chlorotic appearance of considerable areas of the upper side 
of the leaf, making it opaque to transmitted light. The organisms 
found associated with this leaf -spot are Fuscsrium heveae, Zygo- 
sporium sp.. and occasionally Scolecotrichum heceae. 
Another disease common to mature leaves took the form of small 
purple spots from 1 to 3 millimeters in diameter, never larger, with 
light gray centers (PL XVIII. A). The centers eventually fall away, 
leaving holes with purplish red borders. The disease resembles on 
a small scale the large reddish leaf -spot caused by Phyllosticta dm n o, 
but the organism found on the margins of old spots was referable to 
Cercospora iieveae. 
In the examination of spots with purple-brown margins about 
1 to 4 millimeters in diameter on young leaves, spores were found 
which conformed to the characters given for Helminthosporium 
heveoe. but there was little evidence that this was the causal organ- 
ism. Similar effects were very plainly the result of insect punctures. 
BLACK MOTTLING OF LEAVES 
It is a common experience to find the leaves of Hevea in the 
forest affected with what appears to be a thin sooty film. A close 
examination, however, shows that the film is not superficial but con- 
sists of dark-colored irregular-branched hyplne of short contorted 
cells beneath the cuticle of the leaf. It is visible on the surface and 
