854 
THE TROPICAL AGRICULTURIST. 
[June j, 1898 . 
facts have been establisheci, yet it is too soon to talk 
of possible preventives or cures — and a cure in these 
cases of parasitic fungi in permanent parts of a plant 
is always a more difficult problem to deal with than 
a prevention. 
Until a complete knowledge of tlie enemy \ouare 
dealing with has been gained, a.ll experiments in 
these directions must be empiric and to a certain 
extent lyisatisfactory, yet it may be well to state 
the facts already learnt and what precautions they 
teach us to take. In the case of the canker the 
malady is due to a specific disease caused by a fun- 
gus which inhabits the growing tissues of the stem, 
and in the pods such a disease caused by a diSerent 
fungus also exists. 
As I have previously observed, the conditions neces- 
sary for the growth of fungi are moisture and heat 
— the heat in Ueylon is always sufficient, but the 
moisture can be to a, certain extent controlled. 
During the rainy seasons the atmosphere con- 
tinues moist where the sun is not shining, but 
when the sun is up, unless the place is too densely 
shaded the atmosphere must speedily become too dry 
for the germination of spores. It is thus most impor- 
tant that a minimum of shade should be employed — 
the amount of shade necessary for the profitable culti- 
vation of cacao — to prevent attacks of Helopeltis, to 
protect from wind, and other reasons are questions 
which experience in planting shows, and which I will 
not presume to advise, but from my point of view, as 
far as the canker is concerned, this shade should be 
reduced as far as possible. 
It also follows from the observation already made that 
a great risk is run by allowing any bark on which the 
sporophorse or spore-bearing portions are present to re- 
main on the trees, and all this should be destroyed by 
burning, which is the only absolutely effectual means of 
ensuring destruction of fungi. This also applies in the 
case of the pod disease, which should be stamped out if 
care is taken to destroy the husk of every pod as soon 
as it is observed to be attacked. 
Any report until the life history of the fungus has 
been entirely observed, and the rate of growth of 
its different stages determined is, to a certain extent, 
unsatisfactory, and therefore it is of great import- 
ance that those interested in the cacao disease should 
remember that this is only a portion of the result of 
an investigation carried on as far as is possible on 
scientific principles, and that hasty conclusions on 
data more or less incomplete, are not likely to materially 
help in the eventual elucidation of the questions of 
prevention and cure. 
^ J. B. CARRUTHERS. 
March 26th, 189S. 
additional note as to expemments. 
On many Cacao Estates the superintendents reading 
this report may be inclined to themselves help on this in- 
vestigation, and, therefore, a few remarks as to experi- 
mental work which they could do may be of use. 
The most importaut point in carrying out such 
experiments is exactitude in recording what has 
been done, and after observation ryhat the effects 
are at regular and frequent intervals. No doubt 
much useful information v/ill be gained if 
the data are carefully recorded, and it is hardly ne- 
cessary to specify the exact knowledge to be got by each 
experiment. I will therefore briefly state one or two 
examples of how to treat such cases. 
1 . To cut out carefully the whole of a cankered 
part taking care that no discoloured tissue remains 
behind and leave the wound so made to the drying 
influence of the air, and also, if possible, to take a 
stem which gets direct sunlight on it. {Neither of 
these experiments of course could be expected to suc- 
ceed in thick shade). 
2 . To cut as in No. 1 and treat the wound with tar. 
g’ To cut as No. 1 and treat with Bordeaux 
mixture as recommended by Mr. Willis in his re- 
*^Copper Sulphate (Blue stone) . . 6 lb. 
Quick Lime . . • . . . 4 lb. 
Water •• •> ••45 gallons. 
4. To scrape the cankered parts without entirely 
cutting them out and apply the mixture. 
5. To cut out strips about one inch apart and 
about one inch in breadth in the cankered parts and 
treat as before. 
In all the oases of using copper sulphate as a fun- 
gicide, its liability to being washed off is a difficulty, 
and experiments with regard to modifying this are 
importaut. They may, however, be left to the ingen- 
uity of the individual experimenter if it is always re- 
membered that the basis of the application must 
be the blue stone. In France molasses have 
been used, and this mixture resists the action 
of the rain remarkably well, using only one 
tenth of the weight of molasses to that of 
copper sulphate. Dextrine linseed oil and other 
substances have been used, but what is of course 
best is to use a cheap locally produced substance 
which can be readily obtained. 
If these or any of these suggested experiments are 
carried out I shall be obliged if those superintend- 
ing them will communicate with me, so that I may 
take advantage of the information gained and also, 
if possible, inspect the trees myself. J. B. C. 
PLANTING NOTES. 
Rubber Tree? as Shade— are discus.sed and 
it is stated that on Arapolakande in tlie Kalu- 
tara district, trees ten years old along the road- 
sides, &c, seem to do no harm to tea. The 
Para Rubber iree may be different ; but the 
e.xperieiice gained of mixing Rubber (Ceara) trees 
and other products in the Dumbara Valley was 
not satisfactory : Mr. Vollar had to cut them 
out as injurious to his coffee and cacao. Tea is 
no doubt a hardier plant; but it would be well 
not to presume, althougli boundary lines of Rubber 
trees might be allowed.— Since writing this, we 
liave had the benelit of the opinion ot an autho- 
rity who knows as much about Rubber on plan- 
tations as any man in Ceylon, and gives it as 
his belief that Para Rubber trees put out in tea, 
if .50 feet apart, do no harm on lowcountry 
plantations. It is well to know this. 
Dr. Morris, c.m.g., &c., of Kew has just 
delivered (April IStli and 25th) two of the Cantor 
Lectures before the Society of Arts taking for 
his subject “ Sources of India-rubber.” Dr. Morris 
is gootl enough to send us (specially for the Tro- 
pical Agriculturist) concise summaries of both 
lectures; but meantime the following Syllabus 
of the Course will shew their interest and com- 
prehensiveness : — 
Lecture I. April 18. — Distinction between caout- 
chouc and gutta-percha — Occurrence of latex in plants 
— Constituents of latex — Natural orders yielding 
caoutchouc — Methods of extraction — Coagulation of 
latex — History of india-rubber — Progress of industry 
— Imports into United Kingdom — Relative production 
in foreign countries and British possessions — Uses 
— Value of total trade — Forms of commercial india- 
rubber — Present yield — Future supply — Para rubber- 
trees — Geographical distribution — Conditions of growth 
— Yield— Quality of rubber — Methods for collecting 
and preparing rubber— Commerce in Para rubber. 
Lecture II. April 25. — Peruvian and Bolivian 
rubbers — Castilloa elastica — Conditions of growth and 
exploitation in Mexico, British Honduras, Guatemala, 
Nicaragua and United States of Colombia — Venezuela 
and Guiana — Mangebeira — Manicoba or ceara — Matto- 
grosso — African rubber plants — Distribution of Lan- 
dolphias — West African — East African — Mozambique — 
Madagascar rubbers — Lagos silk rubber (A'ciArta)— 
Methods of preparation — Present condition of industry 
— Commerce — New sources of supply — Assam — Penang 
— Sumatra — Java — Borneo — New Guinea — Fiji— Cul- 
tivation of India-rubber plants — Prospects in Mexico, 
Brazil, West Africa, Ceylon, Malaya, 
