45 
produced to effect defoliation. So far this abnormal leaf-fail has not 
been recorded, oi’ at any rate I have not seen any cases of it, in this 
country. 
The leaves of nursery plants are attacked by several fungi but 
none of them are serious and I do not consider it necessary to 
describe them in detail here. 
Two fungi are commonly found on leaves which turn brown or 
yellow at the edges, Gleosporium albo-ruhrum and Phyllosticta 
ramicola. These will be referred to later in considering stem 
diseases. They do not cause serious diseases of the leaves. 
Cephaleuros sp. 
This alga which is found commonly on the under sides of leaves 
where it produces small brown spots has no economic importance. 
The “ red rust ” of tea, a serious disease in India, is caused by a 
similar Cephaleuros. It is worth noticing in passing that such 
an alga has been found penetrating the leaf tissue of Hevea as most 
diseases associated with the tea plant are also common to Hevea. 
No leaf diseases have any economic importance. Fortunately, 
no fungus belonging to the family TJredinese has been found on 
Hevea leaves. It is to this ^family that Hemileia v astatrix, the 
cause of the well-known coffee leaf disease which ruined the culti- 
vation of coffee in Ceylon, belongs. It is quite possible that a 
member of this family might adapt itself to the leaf of the rubber 
tree and might even have equally devastating effects as Hemileia in 
Ceylon but at the present time that does not seem probable. 
The consideration of leaf diseases need not keep us any longer. 
Owing to the particular nature of the leaf it is, perhaps, naturally 
not particularly suitable as the host for parasitic fungi. 
DISEASES OF THE STEM. 
Of the stem diseases now recorded in this country the most 
serious are those caused by Corticium salmonicolor (pink disease), 
Phytophthora faberi (bark canker), Phytophthora species (causing 
decay of the tapped surface) and Botryodiplodia tkeobromat (die-back). 
Other fungi causing disease are Phyllosticta ramicola , Gleo- 
sporium albo-ruhrum (forerunners of die-back), Cypliella hevefe 
(thread blight) and the abnormal condition of the stem, which I 
must include here, caused by burrs. 
Pink Disease ( Corticium salmonicolor). 
In Java and in this country this disease is exceedingly common. 
The disease was very fully investigated in Java by Zimmerman 
Zehnter and Rant, and in this country by Brooks and Sharpies. 
The literature obtainable on this subject is considerable and in 
compiling a summary for purposes of discussion I must point out 
that this literature gives a very complete account of the disease. 
