jn en 
Hevea-trees in the experimental garden of the Laboratory for Agricultural 
Chemistry at Buitenzorg. The trees were under observation during two 
years. The red cankerpatches disappeared wholly during that period, the 
burrs on the contrary increased in number and size, or appeared on trees 
which were originally free from burrs and had only a cankerpatch. The 
other trees in the garden, where no symptoms of canker had been found, 
remained free from burrs. 
Apart from this direct proof, that burr-formation is a symptom of canker, 
this is made highly probable by the fact, that burred trees are te be found only 
on estates where canker has been prevalent, and that no new burred trees 
are added to the existing ones, when adequate measures against canker 
are adopted. 
Treatment of a part of the named trees lead to the following conclu- 
sion: under the favourable circumstances of the experimental garden light 
attacks recovered by itself, provided tapping was stopped, severe attacks, 
when not treated, recovered only in exceptional cases, but by shaving all 
diseased bark, 5 out of 8 badly diseased trees FRONT 
For other kinds of burrs vide sub VIII. 
IV. Comparison of pure cultures of six species of Phytophthora show- 
ed that morphologically P. Faberi (from Cacao, Hevea and nutmeg), P. 
Nicotianae (from tobacco), P. Colocasiae (from Colocasia) and P. Jatrophae 
(from Jatropha Curcas) are distinct species, differing from each other by 
their habitus in pure culture ard by the form and dimension of the conidia. 
P. Fagi and P. Cactorum are quite different from the four species men- 
tioned. P. Jatrophae, P. Fagi and P. Cactorum formed oöspores in pure 
culture; those of P. Jatrophae were not of the Cactorumtype, but of the 
infestans-type. 
V. The result of 390 infections with the six Phytophthora-species 
on different hosts confirmed the result of the morphological investigation. 
The Phytophthora's from Hevea, Cacao and nutmeg belong to the 
same species; only the line isolated from Cacao proved to be more virulent 
for Cacao and Hevea and the one isolated from nutmeg more virulent for 
nutmeg. 
Infections with each of the named species are only successful on their 
own host. With P. Jatfrophae no successful inoculations were obtained, 
not even on „djarak” (Jatropha Curcas) from which it was isolated. 
VI. As to the treatment of canker preventive measures are and remain 
the most important ones; first of all thinning out, next drainage and re- 
moval of intercrops. Pruning for this purpose is not done any more. 
The direct measures consist only in excision of the red cankerpatches 
and the dressing of the stripe-canker with Carbolineum Plantarium (20% or 
