THE TROPICAL AGRICULTURIST. 
709 
others were " shuck "; the space inside was heavily limed, slanting holes being made with an alavanga 
and lime put in. By this means lime can be introduced more intimately round the roots than by sur- 
face liming or forking. No bushes have died or appear to be affected without the trench, and some 
of the bushes inside are recovering. 
The question of the effect of Lichens on the stems of tea bushes was inquired about and atten- 
tion given to it. In the first place, Physcia speciosa, Fr., a lichen with a leaden blue coloured flattish 
thallus bearing on the under surface black hairs, was observed. This lichen is found on exposed 
branches and stems not protected from the sun and rain, and thus is commonest on the less vigorous 
bushes. It is not parasitic on the living tissues of the tea plant, and can be cultivated on glass or 
stone, if suitable conditions are obtained. It gets its nourishment independently of the plant on the 
surface of which it lives, it does not prevent leafbuds from being formed, and it is probable that its 
habit of growing on exposed older portions of stem and branches has originated the belief that to its 
effects are due the lack of vigour of the bush on which it is seen. Some of the less conspicuous 
lichens which lie closer to the bark will be investigated and the results mentioned in a future report. 
That lichens and other epiphytes are a sign that the best conditions for the tea are not present is in 
most cases ti^ue, but their removal at more or less cost does not take away the reason for any lack of 
vigour in the bushes on which they gro w. 
Several inquiries relating to cacao canker, Nectria sp., both on stem and pods, have been 
received and advised on. In more than one case it has been sent as an entirely new disease which 
has not been noticed or heard of by the cultivator before. The life-history of the canker having 
been worked out and the methods of counteracting its evil effects having been laid down, and during 
the last two years carried out with a large amount of success, it is most important that all growers of 
cacao, either European or native, should be on the constant lookout to detect the first appearance of 
this fungus and take steps to get rid of it before any sei'ious loss has accrued and its removal becomes 
a more difficult and costly matter. Their neglect is also a serious injury to other cacao planters. 
Other work in regard to cacao is mentioned later. 
In connection with the investigation of Pestalozzia, the leaves of some thirty or forty different 
jungle and garden plants attacked by ftingi have been examined, but in no case have the spores of 
Pestalozzia been found, though in all cases badly " grey-blighted " tea was near or around the plants 
searched. The injuries which in most cases by their similarity in appearance — to the naked eye — 
with grey blight being due to other causes, it is important, from an economic point of view, that any 
invasion of another plant other than tea by the Pestalozzia should be noted and measures taken to 
prevent increasing the amount of the disease. Seedlings have been submitted suffering from 
" damping," a disease caused by a fungus, Pythium De Baryanum, Hesse, which spreads with great 
rapidity through a bed, generally so damaging the young plants at the " collar" that they fall down. 
It, as a rule, implies that the seed bed is too damp, and where it is noticed all dying and dead seed- 
lings should be taken out of the bed immediately. Before the bed is again used it should be sterilised 
by thoroughly baking all the soil, either by burning bushwood above it or by heating it piecemeal 
over a fire on a shovel, in order to kill the spores of this and other fungi which grow with great vigour 
and rapidity in the soft tissues of seedlings. 
In sending diseased plants or parts of diseased plants for diagnosis it is important that the 
specimens sent should show as far as possible the different stages of the disease and not only the 
last stage when the plant is killed ; also that the conditions and environment of the plants diseased 
should be given and any special circumstances which may have affected them. 
All diseases of plants are the effect of a conjunction of many factors, and the most essential 
and prominent factor is called the cause, as in the case of parasitic fungi. It is often not sufficient 
to know only one of the factors causing the lack of health ; we must know what other conditions are 
concerned in the effect produced. 
The work of a pathologist and therapeutist is to learn all about the life-history and habits of a 
fungus or other organism which has an injurious effect on a plant, and by studying the relationship 
between it and its host and the conditions and environment which encourage it, to discover at what 
time and by what means the prosperity of the parasite can be most easily interfered with. 
A good many matters relative to the cultivation of cacao and its improvement have been investi- 
gated and are still being worked out. Two of the most striking things in the cultivated varieties of 
cacao are the amount of blossom produced in relation to the fruit ripened and the number of small 
fruits, from half an inch to four inches long, which die off without being attacked by any specific disease. 
In some cases the weight per tree of these withered fruits has been found equal to ten to 
twelve ripe pods. This waste energy is clearly a disadvantage to the attainment of greatest profitable 
yield in a cacao tree. 
