8(58 
THE TROPICAL AGRICULTURIST. 
[JONE I, 1894. 
I palled up several sick bushes with the view of 
minutely examining the'r roots. All, from the largest 
to the smallest rootlets, proved healthy and without 
a trace of any alteration. 
, Conseqiieiith/, the disease is located in Vie oveigrowu 
parts of the Coffee-tree and princijpallij in its leaves. 
\ Such are, in a few word', the results of a mi- 
croscopical examination of hundreds of infected 
stems; The spots on the leaves vary in number, 
shape, size and colour. Some leaves showed only 
two or three spots, others were literally covered with 
them. The spots generally take a circular or oval 
shape, semi-circular or semi-oval when they en- 
counter the margin of the leaf : in rare instances 
they possess an irregular contour. Their dimensions 
vary from scarcely the tittle of a millimetre to eight 
or nine millimetres in diameter. The colour changes 
from brown to gray and white, and these shades 
correspond to the difference in the age of the disease 
The distribution of the spots in each leaf is irregular: 
all the parts of the lamina were equally infected. 
The spotted branches are the sprouts of the year : 
the spots are met with in the internodes as well 
as in the junction of the leaves. 
The infecteii berries are at times isolated, at 
other times numbering two or three on each bunch. 
As the peduncle is almost always diseased, it is 
easily understood that an affected cherry quickly falls. 
The microscopic examination of the spots, whether 
of the branches, of the leaves, or of the cherries, 
demonstrates that all depend upon one and the 
same disease. For greater clearness, I take as the 
object for examination a spotted leaf, with the 
naited eye, or letter with a good lens, in the two 
faces of a spot circular concentric spaces are to be 
noted, for the most part with a wonderful regularity 
at a distance of one millimetre. Moreover, and 
this is the chief point in the diagnosis of this dis- 
ease — there are to be seen in the tw >, though more 
generally in the upper, superficies of the spotted 
leaf, thin, white and erect threads of one to four 
millimetres long, and terminating in a cupola of a 
yellow olive colour. The spots on the branches and 
on ^ the cherries also show these same germ-bearing 
threads. 
The disease, then, appears to owe its origin to a pa- 
rasitic fnng us, of a contagious and epidemic nature- 
AU the pathological characteristics, then, noted 
above, are of easy explanation by the morphology 
which I know of these little destroyers of so many 
other vegetables. 
The spore (seed) of the fungus, whether carried 
by the wind, by the rain, or by whatever other 
means, and deposited on the surface of a healthy 
leaf, or on other parts of the plant liable to be 
injected, penetrates into the interior by the stomata 
and produces filaments which spread among the 
cells of the parenchyma. This is the first phase 
of its development, and of the proto-mycelium and 
of iihe mycelium. Bxteriorily only a light brown 
spot is noticeable, the result of the first disintegra- 
tioti of the parenchyma. But the fungus continues 
td spread, and soon there appear on the exterior 
surface certiin filaments {hyphoe), whose apex bears 
the reproductory organs (conidia). Then the fungus 
has run through the various periods of its life and 
perishes, after lhaving scattered a prodigious number 
of spores. In the leaves the spots become trans- 
parent: the tissues invaded by the parasite die and 
dmppear leaving a hollow in the lamina. 
It ia necessary to make a short digression here' 
In the investigation of the cryptogamic diseases 
that attack cultivated plants, it is most important 
to_ ascertain whether the fungus is the cause or the 
cmsequence of the disease, or as we say, whether 
it, is parasitical or epiphytal. The following ex- 
amples will explain the difference that exists between 
the two groups. For a long time past higher fungi 
belonging especially to the genera Agancus and 
Pplypwus have been observed on the trunks of the 
Coffee-trees. These fungi live upon the detritus of 
the bark of the old stems and of the lichens and 
tU9S99S T^hicb Qlvtbe them ; but tbe^ possess theif 
own and independent life, and' the Coffee>tfee only 
serves them as a, sulmtratum, for support. Bach fuu- 
gases are epiphytal, and cause no iateraal dieori«r8 
iu the Coffee-tre'-. On the other h&iid, there exislk, 
in BOLue regions of tropical Asia, a microscopic fancus, 
which prodares in the leaves of the Coffee yellow 
spots, which spread in concentric rings and end 
by hastening ihe fall of the leaf. This 0Bg»niiiui 
is the Uemilvia Vajitairix, and haa ctubed in 10 year* 
a loss of 12 to 1.0 million poan 's sterling to the 
producers of Coffee in the island of t eylon. This 
fungus tben affects disastrously the existence of its 
supporter, the Coffee, and causes its destroction : 
it is a parasite. Notice th«t 1 mention it as the 
unique example of a parasitical fungus, and that, 
happily, it cannot be compared to the fangus wbioh 
attacks our Coffee-tree, and of which cKia commani- 
cation specially treats. 
On weighing that sentenc', it is not enough now- 
a-days to assert that such and sucli a fangas is 
parasitical, simply because of its mode of living 
and of the iujories it causes : the s'tentific proof 
is needful. 
This can only be established by means of sowing 
the spores of the fungus upon a' healthy leaf of a 
C ffee-tree, itself also completely healthy. I under- 
took this delicate experiment, inoculating the disease, 
with which we are occupied, upon a robust shrub of 
Coffee, cultivate 1 in the garden of the Govenuaent 
Observatory. At the time of writing these lines, I 
have nevertheless not been able to verify the results ; 
but directly the characteristic spots appear upon 
the infected parts, we can hold ourselves convinced 
of the favourable termination of the experiment, 
and for that matter of the parasitical nattire of the 
fungus. 
This experime'it will a'so have another advantage 
that must not be despised, and that is, to convince 
the practical man of the true cause of the devastj- 
tion. In all countries and at all times the planter 
has never had much faith in the investigations of 
botanists and especially of cryptogamists. The rustic 
needs a powerful stirring ap of his intellect to 
cause lim to comprehend that, in the immense 
family of Fungi, the number of minute ones is 
greater than that of the large kinds, that the 
harmful surpass the innocuous, and that amongst 
these destructive parasites some attack even our 
poor humanity. All these ideas are with difficulty 
explaine'l to the masses, and consequently it ia 
absolutely necessary always to proceed with due 
caution. It so happened, in the course of my in- 
vestigations, I had an opportunity of talking with 
an old planter, who assured me that this disease 
had always existed in the country. In that 
case, Mr. Minister, we can repeat the old say- 
ing i^ihil sub sole novum (nothing new under the sun) 
and console ourselves. But I hasten to say that in 
the same Coffee-trees, I met with disturbances other 
than that whose study you have commissioned me 
with, that these display certain marks of antiquity 
and that they could easily be confounded with 
the latter. Thus, the other disease revealed itself 
by blackish spots in the leaves, whose superficies 
attained to 1 to 2 square centimetres. Between 
th.e epidermis and the parenchyma of such leaves, 
I discovered a caterpillar and a deposit that gives 
its colour to the spot. This disease is rarer, and I 
have not found a single Coffee-tree seriously damaged 
by it. Other leaves were covered with a light 
ferruginous film, especially along the length of the 
nerves, In others again, the cuticle was clothed 
with a grayish deposit that also attacked the cherr>-. 
I was not able to discover the cause of these al- 
terations. I also verified in the Coffee-trees the 
presence of numerous insects, vrithout being able 
to decide whether it was accidental or whether they 
were true enemies of the bean. The most frequent 
amongst them are the Acarides, the Aphides, and the 
ants. Finally, I have very often see leaves whose 
limb appeared partially burnt. It might well 
happen that drops of water should, under a fierce 
sun, aijt as ^igning-glasses and produce the above- 
