506 
THE TROPICAL AGRICULTURIST. 
[Jan. 2. 1899. 
On examining some hnndi-eda of diseMel pod?, the 
fiinf<i lire in pr^ACtically every case found assocmted. 
The explanation of this Beeui to be that the P.-roao3- 
pora fungus (which belongs to a group most of 
which are parasitic i.e., growing on hviiig tissue, but 
which also has some members which are suyrophytic. 
i,c., growing on dead tissue) at once i-uc^eeds ihe 
canker fungus and lives on the tissue killed by it. 
This I have endeavoured to prove, but have not, up 
to the present, been able to do, owing to the difficxiUy 
in isolating the Perouospora spores fo as to get a. 
pure culture of them for the purposes or inoculation ; 
and so I have not been able to observe the action of 
the Peronospora spores alone on n healthy pod. Ihe 
action ot the canker spores alone I liave been able to 
observe on a heallhy pod, hut in the space of about 
two hours, it was joined by the Peronospora fungus 
and spores of this latter produced. 
The characteristic biown patch which is very moist 
to the touch when cut, caused by the presence of 
these fungi on the pod is more frequently found at 
the ends than on the middle parts of the pods, ihis 
is due to two or three causes. 
In the first place the central tissue of the po-J is 
frequeutlv the means of conveying the mycehum 
of the fungus from one end to the other, and 
this is always the case when the stalk is affected. 
On cutting open a p:)d diseased at both enda 
or the stalk and point diseased longitudinally, the 
central tisue bearing the seeds will be seen to be 
diseolored owing to the presence of the mycelium 
of the fungus. There is also a greater tendency for 
the spores to germinate at the stalk end or the point 
than on other parts— at the stalk end there is a 
naturally-formed cup round the stalk, which retains 
moisture longer than the sides of the pod, »ni at 
the tip a drop is often formed, which remains for 
a sufhoiently long time to enable a spore to germinate 
and nush its germ tube into the tissue of the pod. 
In observing the general effeci of the pod oisBise 
all over an esiate, one finds that the diseased pods 
are c'recirious ou individual trees, so that on one 
tre9°ten or twelve diseased pods are seen, and none 
on the neighbouring trees; while on a tree at some 
litUe distance again there are a number ot diseased 
nods This is more marked where the trees are grown 
at a reason .ble distance apart. This is mainly due 
to the nipid spread of the disease from pod to pod, 
the spores being produced in a few hours, and con- 
veyed to the nearest pods which they, in their turn, 
affect and produced more spores. 
The spreading of 
THE srOBF-S OVEK AN ESTATE 
is a most interesting and the moft importiut question 
in relation to the canker, and has received a great 
deal of thouglit and attention from me, as it is, by 
means of the spores that all the increase of the 
disease comes about Though I have seen . cases of 
infection fiom pod to stem and vice versa, by actual 
contact, these cases are so rare, that we cau neglect 
them and consider that the spores are responsible 
for all the extension of the disease. 
The methcds of infection of different trees are 
very various ; but we can distinctly point to three or 
four chief means of attack which have l>epu cons- 
tantly observed. In the first place, the wind has no 
doubt tlie largest share in spreadina the sporss, es- 
pecially over large distances, and it is the wiuu which 
enables the disease to spread from estate to estate. 
Instances of this may be mentioned. In one case 
an estate was chiefly and first attacked a: the point 
nearest to a native garden which had been entirely 
killed out by canker, and the trees allowed to remain 
after they were dead ; a prevalent wind blowing from 
this direction. Cases similar to this are numevou-. 
On the other hand, the disease is ot^en absent from 
sheltered hollows, even though there were present all 
tha conditious which favour it, because the. wmd 
passed ri<'ht over, and not through the cacao. 
The next and nearly as important an agent is 
water-both rain and river. Ram w'snng 
down the trees and dripping cff the pocs on 
to other pods or parts of branches and stems, carrie 
with it the spores from infected places, and leaving them 
crtusea f r( th epots. I have seen a tree covered with 
a mass of smal^ fretli diseased places all independent 
of each other, below a,u olJ paich of ''anker, wi.ich 
was covered with spores. Tbero h ive bteu many 
and clear proof of livers apreading the disease. lo 
some cases, Ifeir, by the dead limber being thrown 
into the Btreaui and co veying its dendly cargo to 
other places lower down: and also a number of 
instances of cases of flood washing the spores over a 
flat area of cacao and infecting the trees. A very clear 
case of thiB was found in one young cleariug where 
practioallv every tree was cankered just above the 
6urf4ce of the ground, where a few iuchea of wa'cr 
had stood for a short time during a flood. 
JUit, in addition to both, wind and water, ants and 
other small animals are the means of hpreiding the 
disease ti au extent that I think is hardly recog- 
nised. Anyone who has watched the coaselesa 
activity of ants in running over stem, branch, and 
pods of cacao tree, cannot fail to see how they mnet 
be the means of carrying from one pla«e 
to another ihe spores when they pass over 
theni. I have examined the legs and bodies of 
some ants which had been travelling over a tree 
having spores on its bark, but without discovering 
these spores ou them. But, considering the extremely 
small size of the spores, this does not materially 
weaken the contention, and, indeed, I should have 
been surprised if in any of the few cases I examined 
I should have discovered any spores. The fact that 
the ants frequent the pods 'where they feed on the 
secretion from the backs of the white cotidas that 
live on the juices of the pod alone, makes it probable 
that in the case of the pods the auts are responsible 
tor a good deal of damage in carrying infection. 
How much part 
THE PODS 
take in spreading the canker in comparison to 
tha stem and branches, it is very hard to 
determine, but the rapidity with which the fuugoa 
grows in the pods, produces its spores, and 
spreads to other p:ds and to the bark, leads 
to the supposition that in m iny cases the majority of 
the damage is due to the dise.ise in the pods. It is 
unfortunate that in most estates the time when the 
largest number of poda are on the trees is the wet 
season which is most favourable to the fungas, and a 
suggestion may be offered in this connection ; it is 
well known to cacao planters that the amount of fruit 
produced by each tree at the different crop times 
varies ; that one tree produces a bigger spring crop 
and not so big an autumn one as another — this is an 
individual characteristic which is in many cases quite 
pronounced. If such characteristics are carefully 
selected in propagating (as had been done to pro- 
duce the early and late varieties of cereals and many 
other cultivated plants), a planta ion miy be formed 
which will, in normal seasons, habitually produce its 
1 irgest yield of fruit in the spring when the dangers 
of attacks of fungi are much less and when the 
planter has the advantages of sun in ripening his 
pods and curing his seeds. By continually using seed 
which has been produced in the spring, no doubt this 
would be gradually done ; but it would be more 
effectually and quickly brought about, if the planter 
would observe for a year or two those individual 
trees which bear their fruit more in the spring, and 
by using the seed from them, get in time a spring 
crop variety. The attention of planters might also 
with reason be drawn to the practice of grafting 
which Mr. Hart, of Trinidad, has shown to be prac- 
ticable ill cacao, and which would, without doubt, 
lead to most interesting results. 
With regard to 
THE CUEATIVE EXPEBIMENT3, 
the interest of my stay over the wet season has been 
to me very great, for I have been able to visit 
some ten estates in different districts, in 
all of which curative treatment has been car- 
ried on, and in all eases the treatment 
has been to a great extent successful. It must 
be remembered that in the previous reports 
