• Dec. 1, 1902.] THE TROPICAL AaPJCULTllRIST. 377 
that shewn in Fig, 8. No further development was 
noted in hauging-drop?, except that the thicks\ ailed 
oil contniuing hyphae became daik brown (hree weeks 
after sowing, and apneared identical with the old 
mycelium desoiibed above in the case of the cine 
Fiingns. Aa in the sugar-cane Fungus, advantage 
was taken of the aerial development of myoelinm in 
single-spore hanging-drops to prepare cultures free 
from Bacteria. 
Iq plate-cultures in the cane extract medium 
R copious development of greyish mycelium was 
obtaiued on the third day, which formed a dense velvety 
pile, a quarter of an inch in height, on the surface of 
the gelatine, and in which dark bodies could be 
detected with the naked eye. When examined on the 
sixth day these daik bodies were found to be pycnidia 
in which paraphyses and spore formation could be 
detected, after the manner indicated in Fig. 9. 
On sterilized cacao and oak-wood small dark bodies 
weie noted in nine days, and these when twenty days 
old proved to be the pycnidia of the Fungas. 
It will be seen therefore that the development, under 
artificial conditions, of the Fungus of the cacao tree 
corresponds exactly in all its details with that found 
on the sugar-cane, so that morphologically regarded 
the two forms are identical. 
It was now necessary to perform infection-experi- 
ments on cacao trees and pods, with pure cultivations 
of the Fungus. 
These were as follows : — 
1. On cacao pc ds : 
(«) Two nearly ripe pods were selected for the 
experiment, and were wnshed with alcoholic corrosive 
sublimate, and ut 'he points where incisions were to be 
made small cavities were made in the rind by lifting 
the surface and cutting out a small portion of the 
tissues underneath. Jnio one of these chambers 
actively growing mycelium, three days old and from 
a pure culture, was intioai.ccd i nd the pc d was bonrd 
np with buddii)g-iape. Theoiherpod w,is tieated in 
asimi'ar way. txcept that uomycelium was introduced 
and thus served as a control. Five days afterwards, 
about a quai ter of ihe surface of the infected pod had 
turned brown, and in eight days after infection the 
whole of the suiface was deep tiown, and there was a 
considerable d&s'elopment of pycnidia for some dis- 
tance round the point of infectirn. The protrusion of 
the spores as a gi eyish ' tendiil,' visible to the naked 
eye, from the ostiole of the pycnidium, and their 
gradual daikening were beautifully shown on this 
pod. iNear the point of infection the spores were 
visible as a b'ack dust on the surface cf the pod, and 
inmost cases the ' te ndrils ' had broken down into 
their constituent eporef, each showirg ilie traraverse 
wall aijd ti e dajk-biown colouration under the mic- 
rofcope. Further away the colour of the fpores 
became lighter and ' tendrils ' were more numerous 
The S3 were composed of spores loosely cemented 
together, in which the transverse wall had not yet 
appeared. The conliol pod in this c-xperimcnt showed 
no ihfectiou. 
[h) The above preliminary experiment was repeated 
and in thiscase two nearly ripe pods were infected 
with mycelirm, ar.d a third wes used as a control. 
Distinct infection took place in three days while the 
control gave negative results. 
[c) Kext, for ha f-giown pods were selected for 
experiment, in older to determine whether the spread 
of the Fungus is as rapid here as in nearly lipe pods. 
In each case small cavities were made in the rind, 
and in the first pod ripe spores fiom the infected pod 
in experimeut {a) above were placed in the cavity. 
In the secon.'i pod a portion of the lind contain ng 
growing m.^ceiir.m fnmthe infected pod (o) above 
was introduced, and in the third pod a^ilively grow- 
ing mjctlitnn frcm a pure culture was nstd fcr 
infection. The fourth pod served as a control. 
Seven days afterwards distinct infection was ncted 
■ in the first pod, the rind having turned brown 
about a quarter of an inch all round the cavity, and 
in the discoloured tissue mycelium was extremely 
abLuidant. In the second pod infection had proceeded 
further, about one scpare inch of the surface being 
attacked. In the third pod about six scjuare inchea 
of the surface was decayed, and it was found that 
the mycelium had penetrated to the mucilage sur- 
rounding the seeds and had completely invaded the 
interior of the pod. iNumerous pycnida were observed 
utider the epidermis near the point of infection. 
The control pod gave negative results. This experi- 
meut is of some interest aa it throws light on the 
steps by which a saprophytic form may gradually 
become parasitic, and confirms previous observations 
on the infiueuce of a nutritious food-material in 
increasing the activity of a Fungus. 
{i/) Next, a preliminary experiment was performed 
on l-vo nearly ripe cacao-poJs, in order to determine 
whether infection could be produced by spores without 
previously wounding the rind. A drop of sterile water 
containing spores was placed on the surface of the 
pod, and was covered by a small glass cell which 
was sealed on to the rind by means of rulaiug wax. 
The cell was covered with a dark bandage to shield 
the spores from direct sunligtit. Seveu diya after- 
wards the spores had developed a mycelium on the 
pod, but peuetration of the intact rind by mycelium 
was not noted in either case. Unfortunately time did 
not permit of carrying out furtherexperiments to settle 
this point definitely ; but a consideration of natural 
infections seems to indicate that pods at any rate are 
cap ble of being infected by germinating spores 
directly. If this were not the case ic is diliicult to 
explain why infection almost always begins at those 
points on the pod which are moist for the longest time, 
viz. the free erd of the pod, the groove at the insertion 
of the stalk, and the place where pods come in contact 
with the branchea. 
2. On the cacao trees : 
In the infection-expeiimects performed on the 
cacao tree itself, a small portion of the outer dry 
hoik was carefully removed and the exposed bast 
washed with sterile water. A small chamber was 
made by laising the baik and cutting out a small 
portion of the bast down to the cambium. After 
intioducir.g the infecting material, the barklid of this 
chamber wi^s depressed and the whole covered with a 
water-tight bai dage of budding-tape. The control 
plants were treated in the same way, except that no 
mycelium or spores were purposely introduced into 
the cavity. 
(a) Two branches of a healthy cecao tree were 
selected for the preliminary experiment In one 
cavity actively growing mycelium in the cane-extract 
medium was intioduced, while the other branch waa 
used as a control. Eight days after infection the 
Fungus had killed (he bast np to about eight inchea 
above and below the chc.mber, at which point the 
blanch was nearly ringed. The mycelium could be 
traced ruoie than a foot above and below the 
chamber, both in the bast and in the 
wood, and to a considerable depth in the 
latter. Numercus pycnidia were developed under 
the attacked bark, some of which were liberating 
their spores. The control showed no infection. 
(i) Bight healthy cacao plants about eight months 
olr"', growing in bamboo pots, were next selected for 
an expeiiment. Nos. 1 and 2 were infected with 
spores taken from a pod attacked by the Fungus, 3 
and 4 with portions of the diseased rind of a pod con- 
taining Ectively growing mycelium, 4 ana 5 with 
vigoi ous my celium from a pure culture in cane extract 
and 7 and 8 were control plants. After binding up the 
wounds the plants were placed in the shade and 
watered daily- Eight days afterwards it was found 
that infcclicn had taken place in all the plants fiom I 
to 6, while the control plants showed no infection. 
There was scarcely any difference in the .'mionnt of 
infeciion when spores or diseased cacao-pod rind were 
used, except that plant No. 1 was killed outright by 
the Fungus. When culture-mjcelium was used 
