60 
Sach’s water-culture solution alternated at intervals of seven 
or ten days with rain water. Controls were kept in all experi- 
ments, and the viability of the inoculum conidia was tested in 
hanging-drops. It was found that the leaf-inoculations were far 
more successful than any of the others. In fact, eleven out of 
twelve leaf-inoculations gave positive results, while only one out 
of thirty-two of the others was successful. At a later date, two 
further series of leaf-inoculations gave 100 per cent. positive 
results. Older tougher leaves were as susceptible as younger 
leaves, and the upper surfaces as the under. The first signs of 
leaf-infection were noticeable after fifteen or sixteen days, and 
the mycelium of the fungus was traceable through the leaf- 
petioles into the stems. Later, numerous acervuli developed on 
the twigs bearing the inoculated leaves and on the leaves them- 
selves after about ten days in a damp chamber. The one 
successful stem inoculation was made through a punctured 
wound in the growing point. Twelve days after inoculation, the 
stem apex began to blacken. This was followed by the collapse 
of the apical pair of leaves and by the extension downwards of 
the discoloration. Colletotrichum was afterwards recovered from 
the affected stem. 
A full discussion of the significance of Colletotrichum in 
connection with coffee dieback need not be initiated here, for 
details are to be found in the publication referred to.* Suffice 
it to say that the infective conidia of Colletotrichum coffeanum 
have been shown to be common in the atmosphere and that they 
have been proved capable of invading the coffee tree, and to 
note that the conclusion has been arrived at that Colletotrichum 
coffeanum is not an aggressive parasite of the coffee tree, an 
that it need not bring on attacks of dieback unless the conditions 
for its advance are rendered favourable. That this is so has 
been proved in practice. Unfortunately a survey of the history 
of coffee in Uganda shows that the crop was often not as able as 
it might have been to resist attacks of Colletotrichum. The older 
trees were seriously weakened by leaf disease (Hemileia vastatriz, 
B. and Br.) at a time when they were in full bearing of what was, 
in many cases, their first full crop, by the effects of overbearing, 
by neglect of cultivation and pruning, by the lack of attention 
to seed-selection and the necessity for rearing and planting out 
only the best plants, by hurried planting, and by successive 
serious attacks of various insect pests. At the present time, the 
oldest coffee in many cases seems to be still suffering from the 
leaf-disease and overbearing of 1913-14 and to be subject to 
dieback, despite the increased attention that has been given to 
it, while younger coffee which has been brought up, as it were, 
in the light of the experience gained from a study of the behaviour 
of the older trees, is found to suffer from true dieback to the 
extent cf only a branch here and there. The older larger-scale 
* Small: Dieback of Coffea arabica in Uganda. Cire. No. 4, Dept. 
of Agric. 1920. 
