524 
THE TROPICAL AGRICULTURIST. [December i, 1881. 
quantity when discovered. Without, of course, making 
airy positive assertion on what cannot he proved, it is 
very probable that Hemileia was already widely spread 
on the coftee in 1869-70, a conclusion rendered the more 
likely if we reflect how difficult it is to notice new dis- 
colourations on the leaves. 
Apart from the extreme probability, however, that 
Hemileia slowly accumulated on C'qff'ca arabica bypass- 
age from some jungle plant, I proceed to give strong 
objective evidence that such a view is most likely. I 
find, as indeed was already known, that Hemileia occurs 
on a native wild coffee (Cojf'ea travancorensis), found 
in the jungles, and have experimented with the spores 
of the fungus on this plant with the following results : 
they form germinal tubes, block up the stomata, send 
branches into the leaf, and form the mycelium in Cqffea 
arabica, as well as in C. travancorensis ; and, conversely, 
C. travancorensis can be infected by spores from Hemi- 
leia on C. arabica. 
The anatomy of the fungus on G. travancorensis, 
moreover, offers nothing different in any important respect 
from that of the common Hemileia; the mycelium, it 
is true, is usually less highly developed and produces 
fewer spores and less virulent spots in consequence, but 
this depends on vigoiu' and not on specific differences 
of any kind. It is at least probable, therefore, that 
Hemileia vastatrix lurked in the jungle long ere Cojf'ea 
arabica was widely planted on estates in Ceylon. 
About a year ago, however, my attention was directed 
towards another possible holdfast for "leaf disease" by 
finding a Hemileia which had already been collected by 
Dr. Thwaites in 1868, and named Hemileia canthii from 
the shrub on which it occurs (Canthium campanula turn). 
This Hemileia., on closer examination, did not appear to 
me to present sufficient differences to warrant its being 
constituted a separate species. In size, colour, shape, 
and marking, the spores resemble those of the Hemi- 
leia vastatrix ; the structure of the spore-bearing head 
which protrudes through the stoma and the mode of 
origin of the spores are just as before. Unfortunately, 
I was unable to obtain a stock of fresh material at 
the time of these observations, and that in the herbar- 
ium at Peradeniya was 12 years old, consequently no 
sowings could be made, and the evidence was incomplete. 
During my journeys among the estates, however, I 
lost no opportunity of searching for Canthium campan- 
ulatum and its Hemileia, and found the shrub in Diun- 
bara, Pussellawa, Haputale, Balangoda, Badulla, &c, at 
various times. It appears to be a widely-spread plant, 
therefore, but very few specimens as a rule occur to- 
gether. During all this peiiod I only met with the 
fungus in fruit once, though the yellowish spots and mycel- 
ium occurred oftener. 
In January last I commenced experimental sowings 
with spores of Hemileia vastatrix from coftee on .the 
leaves of Canthium plants placed in pots, &c. The 
result was what I suspected — the germinal tubes blocked 
up the stomata, sent their branches into the leaf, and 
commenced to form a normal mycelium hi the inter- 
cellular passages of the leaf, as in coftee. 
In August last, during a journey from Madulsima, I 
had the startling fortune to meet with a fair-sized shrub 
of Canthium badly diseased, and of which the leaves 
were in some cases covered with rust.* The plant was 
on the roadside a few miles out of Badulla, in the 
direction of Passara. Carefully collecting specimens, I 
proceeded to clear up what details I could on the fresh 
mycelium, &c. The mycelium and spore-bearing head 
arc quite .similar to that in coftee, the chief differences 
I i i due to the denser structure, &c, of the leaf in 
Cmthmm. The passages between the veiy small dense 
cells, with thick walls and closely-packed contents, and 
li i worth remarking that a pyrenomyeetous fungus 
occurring as a black crust on many of the leaves is 
very similar to one common on coffee, and interferes 
sadly witli experimental sowings. 
the small total mass of loose tissue in the leaf are among 
the chief peculiarities here. The stomata are also sinalf. 
The mycelium is therefore much less highly developed, 
and it is difficult to detect the thick stumpy branches 
among the crowded leaf cells. In proceeding to form 
the spore-bearing head, the branches meet in the chamber 
below the stoma and fuse into a cellular body, as in 
Hemileia vastatrix ;• but instead of many branches so 
meeting the sparse mycelium here sends but two, the 
fusion of which strongly resembles a definite process. 
The spores are produced in smaller numbers, but essenti- 
ally as on coffee, and the sparse mycelium and spores 
recall what is seen in Coffea travancorensis. 
The germination of the spore occurs readily, and re- 
sembles that of II. vastatrix. I have not succeeded in 
finding teleutosporcs of Hemileia canthii. 
Of course, on obtaining the above specimens, I at 
once instituted experiments to show whether the germ- 
inal tubes enter the coffee leaf. These experiments have 
not as yet been successful so far as to produce disease 
spots and fruit, since so many foreign spores were inter- 
mingled with all my specimens that then more rapidly- 
developed mycelium sadly interferes with germination. 
I hope, however, to conclude successfully before long. 
It may be mentioned here that another possible sourct- 
of the original spores on coffee may be some other host 
plant altogether ; though it by no means follows as a 
necessity that the conidia produced by the teleutosporex 
of Hemileia ever germinate successfully in Ceylon. This,, 
however, is hardly a matter for discussion here. 
Sec. V. — Summary and Conclusion. 
§ 22. I have now placed before you the details of 
what has been ascertained regarding Hemileia and its 
relation to coffee leaf disease, and may- sum up the main 
points of importance as follows : — 
1. — Hemileia vastatrix is a parasitic fungus, the 
spores of which are capable of rapid germination on 
the moist surface of a coffee leaf. The short tubes 
thus produced enter the breathing pores of the leaf, and 
in less than a week, in favourable circumstances, 
begin to form a mycelium which, at the end of a' other 
week or so, have done sufficient damage to the leaf to 
produce yellow spots. During the third week the spores 
are usually produced, each to act, as before, if sown, &c. 
2. — A leaf of the coffee attacked at numerous points 
by such germinatiog spores rapidly succumbs to the 
ravages of the mycelium, and falls long before it would 
normally have done so; not only by directly robbing 
the tree of food prepared by the labours of the leaf,, 
but, further, by occupying space and shortening the 
period of usefulness of the leaf, is the tree injured. 
3. — The loss of matter and functional disturbance 
brought about by these continued and periodical 
ravages have for effect a diminished power to mature 
crop on the part of the coffee; and flower-buds, flowers, 
and berries fall because the nutritive relations between 
the shoots, leaves, and flowers have become over- 
thrown. More crop is borne, as a rule, however,, 
where the trees contain more fo">d material to support it. 
4. — The spores of Hemeleia are carried by wind. 
Whether a spore travels a long distance in one 
journey, or whether it is swept along in successive 
leaps, it may be carried from one estate or district 
to another. The shaking of the trees also dissemin- 
ates spores, and they are driven from fallen leaves 
to the trees. These spores, scattered on the foliage, 
become washed down to the lower surface and germ- 
inate as before, provided the atmosphere, &c, bo 
sufficiently moist. 
5. — No special predisposition on the part of the 
coffee is required for its infection, and no others 
conditions are necessary to the spore than moisture andf 
the presence of air, &c. , as with any germinating seed. U 
6. — The spores are in such countless numbers, [I 
germinate so rapidly, and some of them so easilyll 
