September r, 1888.] THE TROPICAL AGRICULTURIST. 
tree, which causes the bark to rot, gives a mouldy 
appearance to the roots, and spreads itself at a later 
stage upwards along the stem in vertical stripe, so 
that the bark dries up over the whole length 
of each strip, even the underlying wood being 
affected to some depth. The disease ends inevitably 
in the death of the tree if it be left to itself. For 
the purpose of studying the disease, the plan ig 
to cause it artificially, which is not difficult to 
accomplish. With this object a young cinchona tree 
is planted a few centimeters too deep, ('. e«, in such 
a way that the stem is covered with a layer of earth 
to the depth of a few centimeters. After a time, 
shorter or longer according to the less or greater 
moisture of the soil, &c, the tree assumes a sickly 
appearance, displayed by a yellowish tint of the 
leaves, particularly at the top, and by a red leaf 
here and there amongst the foliage. If at the 
beginning of these symptoms the tree be examined, 
the roots will still be sound, but on scraping off 
the epidermis at the neck of the roots, it will be 
found that the immediately underlying tissues have 
acquired a beet-red colour ; whilst iu health they 
are of a light green. If the superfluous earth be 
removed to immediately above the root s, the tree 
recovers perfectly within a short time. But if let 
alone the disease increases rapidly, the neck of the 
root shews a speck of decay, which quickly spreads 
itself downwards amongst the roots and upwards along 
the stem. 
So long as decay is only partial, for instance, ex- 
tending to one-half or less of the circumference of 
the neck of the root, succour is still possible. Let 
the tree be entirely removed from the earth, wash 
the roots clean, so that the extent of the disease can 
he ieen, and cut away relentlessly all diseased portions, 
to the sound layers of wood. It will be found that 
the ends of the roots are all still healthy, and 
that the original seat of the disease was the root 
neck. Diseased roots are best cut off entirely, if 
they are not much too large, and the surface of 
the section should be covered with grafting wax. 
Severe pruning is now necessary, as the above 
described operation naturally disturbs the circu- 
lation of the sap, and withering is to be feared, 
should the tree be allowed to retain all its leaves. 
Replanted, and this time to a proper depth, the 
tree gem-rally remains alive, and often grows after 
its recovery as well as if nothing had happened. 
In spontaneous appearance of canker in seedlings, 
I have invariably found similar symptomB, the seat of 
the evil was always at the neck of the root, whilst 
the ends of the roots remaiued the longest un- 
injured. I conclude from this, that the canker is 
a limple decay of the bark, which begins at the 
upper part of the root, and communicates itself to 
the surrouudiug portion. As the circulation of the 
sap is impeded at the seat of decay, the cellular 
tissues lying vertically above and below the attacked 
place, will be the first to wither and decay, whilst 
the mycelium which is found in fine white threads 
spread over the diseased roots, is probably not a 
consequence of the disease, but only attaches itself 
to the decayed parts, as it does to other decaying 
wood iu a damp under-ground position aud of this 
decay at the neck of the roots, I have been able 
to discover no other cause than that of too much 
moisture. 
This moisture may however proceed from various 
causes. Too deep planting it one of the prin- 
cipal origiuu, and one which by close attention 
can easily be removed. That the stem, which is 
formed to bo above the ground, should decay when 
buried under damp oarth, can surprize no one. 
Kveu though Ti-t planted too deep, the neck of 
tba roots may be exposed to too Much mois- 
ture. The decay of organic matter develops much 
water, whilst besides this the decaying product! 
themsolvoi are very aqueous. If planting ii done 
iu soil too richly supplied with humus, or if too 
much decaying matter ho heaped up rouud the tre«, 
ha ooiisequonce will bo that the surface of the 
ronud remains »onBtnntly surchar^oU with mois- 
ture, of which again decay aud canker become the 
results. Since under these circumstances especially 
the diseased parts are speedily overgrown with 
fungus, of which the germs were already at hand 
in abundance, it often seems as if the fungus 
were the cause instead of the consequenoe of the 
disease. I am of opinion, however, that this is 
erroneous. 
Iu an advanced stage of canker a white, tough, 
fleshy excrescenoe appears between the deoayed 
bark and the wood, aud spreads over the entire 
surface of the diseased parts. As this fungus is 
not, however, always found, and only shows 
itself at an advanced period of the disease, it 
cannot he looked on as a cause, but only aa a 
symptom of the disease. The withering of the 
bark and the decay of the tender paronchyma-cells 
and vessels of the cambium cause an empty space 
between the rotten bark and the wood, which 
space is most suitable for the development of 
fungi, so that we cannot be surprized to meet 
with them in such a position. 
That the so-named canker is nothing else than 
decay seems to be conclusively proved by another 
fact. 
In the case of young grafts it happens here and 
there that the starting point of the disease is not 
the neck of the root, but occurs at the graft joint 
a few centimeters above the ground. This point 
is the most vulnerable part of the stem. The outer- 
edge where the conjoined surfaces of the original 
stem and the graft grow together protrudes like 
a callous rim, of which the tissue consists of the 
youngest formed cells, whilst there « no strong 
protecting epidermis to secure it from injurious ex- 
ternal influences. So that between the grafted slip 
and the truncated stem of the original tree, should 
there be anything remaining of the latter, water 
can readily accumulate which may be forced into 
the grafted slip, by the bark produced by the 
growth of the tree. Thoae who persist in ascribing 
canker to a particular fungus, of which the germs 
abound more in one soil than in another, will 
find it difficult to account for its appearing 
on grafts situated so far above the soil. 
The predisposition of the graft joint to canker 
indicates an analogous danger to cuttings, at least 
in so far as concerns those taken from woody twigs 
and suckers. 
* 
CINCHONA CULTIVATION IN BOLIVIA. 
Dr. H. H. Kusby, of New York, whose lecture on the 
home of the coca leaf we reported a few weeks ago, has 
now also given his experiences in the cinchona district*. 
Like the swallow of the fable, Dr. Rusby has seen much 
and remembers much (or, perhaps, even slightly more). 
Dr. Rusby's statement, that "at the present time no 
bark, except an occasional bale, reaches the market 
from South America whieh is not the product of cul- 
tivated trees," is certainly far from accurate, and his 
description of the dreadful havoc wrought by the felling 
of trees in the forest to make a clearing for cinohona 
growing, though picturesque to the ordinary mind, 
savours of romancing. This is how the Doctor narrates 
the Btory : — " The clearing process is not so difficult 
here (in the mountains) as upon the level ground, owing 
to the ease with which the trees can be made to fall. 
It often happens that the trees in falling will carry 
down immense tracts of forests with them. The place 
where the trees are planted is very steep. On such a 
place I have seen a tree weighted down with water ;ju 
crashing down to a point so far below us that to reach 
it by the road it would occupy au entire day, whereas 
the tree reached the bottom in a single instant, carrying 
with it, not only all the trees aud vines iu its way, but 
immense masses of rock and earth, an avalanche of 
vegetation, blocking up the stream below." 
" Tho trees contain a very great amount of water, aud 
are almost completely covered by parasites. Upon a 
single tree may bo counted sometimes from fifty to ouo 
hundred ditlVrcnt species of p'. utM growing ub pnraaitM, 
so thul tue trunk of the luu which wight be 9 feet in 
