' 
tes 
less). Detection of the disease at an early stage is highly important. Di- 
seased trees are not tapped. 
When done thoroughly this treatment proved a complete success in 
most cases; on some estates, where the climate was favouring canker this 
treatment is not sufficient; new means of combating the disease are to be 
looked for, probably spraying with a fungicide; also the fruit-rot should 
receive more attention. !) À 
VIL Infection experiments with fruit rot are shortly discussed in para- 
graph 7. P. Faberi alone can cause fruit-rot, and even without a wound 
being made before. During the experiments the disease spread in a most 
extraordinary way. When starting the experiment there was not one diseased 
fruit in the plantation; after three weeks the experiments had to be stopped 
because locally 50°/, of the fruits were attacked, many of them being 
quite covered with Phytophthora-conidia. Small flys (Drosophila) seem 
to help a good deal in spreading the disease. / 
VIIL. Four different kinds of burrs in Hevea-bark are distinguished 
according to their origin: ; 
19. Real peas in leaf-scars (Plate VI and IX to the left). These are 
not caused by dormant buds, as the connection with the pith is still 
intact and therefore the bud alive (cf. fig. 1 and Plate VIII). Probably 
these are formed around the remainder of the vascular bundles of the 
petiole (BATESON), as has been demonstrated by HARTIG for the sphäro- 
blasts, which are formed in the leafbasis of fir-trees. These peas are rare 
and harmless. 
2°. Burrs, arising after the use of the pricker; these are built con- 
centrically around the scars made by the pricker (fig. 2). These become 
rarer every year and will soon disappear wholly. 
3°. Burrs as a result of canker; (vide sub III) these are very common 
and often of considerable dimensions (Plate IX to the right: and Plate XI). 
Nearly all the badly burred trees are of this type. The only remedy is to 
prevent or treat all canker-cases. 
1) After this publication had gone to the press, the writer came to the conclusion, 
that it is possible to prevent stripe-canker (black thread disease) absolutely. Experi- 
ments by the writer and the technical staff of the Hollandsch-Amerikaansche Plantage 
Maatschappij have made this point quite sure. 
As soon as the rains set in, every tree is treated daily with a solution of 50/0 
Carbolineum Plantarium or 10% Izal. The first named solution seems to be the best. 
Each tapper is provided with a bamboo or a bottle containing the named solution and 
a brush made from rottan or some other material. After scrapping a tree the tapping 
cut and |, to 1 inch of the renewing bark are dressed with the liquid. This can be 
done within one hour. Daily treatment prevents infection absolutely; treating the trees 
once a week the cases are reduced in number and in intensity. After 4 days of dry, 
sunny weather the treatment can be stopped. 
mr zn 
