THE TROPICAL AGRICULTURIST. [December i, 1881. 
July, as was the case. During July less germination 
went on in the dry weather, but a stock of spores was 
ready for the wet August, and the resulting mycelia 
should (according to experience) produce their spores 
about the end of the month. Such was the case, but 
the " attack was a milder one," partly because there were 
at that time fewer leaves left on the trees, partly be- 
cause the winds had been less active in the interval. 
A second illustration is afforded by an estate in the 
neighbourhood of Badulla. On the 1st January, 1881, 
the coffee was luxuriant in wood and leaf, but during 
the last week in January " a most virulent attack of 
leaf disease " appeared, and a bad fall of leaf suc- 
ceeded it. By the end of February it had " passed 
away," and the coffee set to work to produce new leaves. 
By March 30th the " estate had recovered." The im- 
provement went on through April and May up to June. 
A little Hemileia then showed itself, and during July 
and August a "mild attack" made itself evident. 
The last ten days in December, 1880, were "especi- 
ally wet," with mists and rain all day. January opened 
with fine weather for most of the first fortnight, and then 
the wet weather returned for sixteen days. February and 
March were fine, hot, and marked by thunder-showers 
every now and again. The "virulent attack" which 
came on during the last week in January would natur- 
ally result from the success of spores germinated during 
December, and the fact of its "passing away" in 
February is in agreement with what I have established 
earlier — that the spores accumulated could not germinate 
in the dry weather. 
Another example may be taken from the extreme east 
of Uva, where the worst " attack of disease " came on 
in October and November. 
In Aiigust, 1880, the place was looking fresh and 
green, and a little rain fell. September was very dry, 
and a " very mild attack of leaf disease " was experienced. 
October and November were wet, with a fine interval 
of about a week late in October. During November 
"a very bad attack of leaf disease was experienced, and 
a larger fall of leaf than had been witnessed for years." 
At this period, too, much crop fell from the trees. 
This state of affairs continued into December, which 
was a very wet month. During January, 1881, (the 
weather still wet) the dropping of crop continued from 
the trees still poor in foliage, but a diminution of 
disease was noticed. In February the weather became 
very dry, the remaining bad leaves dropped, and new 
ones commenced to form. This continued through the 
dry March, the new leaves being produced in weather 
when those spores which did get on to them could 
not germinate. In April the coffee had recovered and 
was quite green and luxuriant. But the large masses 
of foliage had now been exposed to occasional access 
of spores for three months or so, and the first spejl 
of wet weather would be expected to cause their germina- 
tion. This happened in May, the first 15 days of 
which were wet, and the consequence was an outbreak of 
the rust in June. These illustrations, read in the light 
of experiments and previous knowledge, show clearly 
enough the nature of the disease and the manner of 
its dependence on climate, &c. 
We are now in a position to inquire further into the 
matter of leaf disease, as it occurs on large areas of cofiee 
such as are found on estates and in open districts. 
Sec. II. — Leaf Disease on laege masses of Coffee. 
§ 9. Perhaps the simplest example of what occurs 
on estates generally is afforded by what happened this 
year to a somewhat oblong patch of coffee trees, 
standing in a slightly isolated position at Peradeniya, 
and on which I have kept close watch for the past' 14 
months. The wind of the S. W. monsoon blows through 
these trees along the longer axis of the group, and in 
such a way that one tree at the end receives the wind 
before the others. 
During January last many of the leaves had fallen, 
and the trees looked thin after the "attack of leaf 
disease" which occurred towards the end of the year 
1880 ; on February 1st, 1881, there was in fact, but 
one pah of leaves at the end of each twig in many 
cases, and no twig had more than two pairs and a 
terminal bud. During the hot February, this end bud 
slowly developed, and before the end of March a second 
end bud had formed and opened ; the average number 
of completed leaves at this time was, therefore, three 
pahs to each twig. 
During the hot weather which prevailed in March, 
these leaves were all dark green, and healthy, and 
scarcely a trace of Hemileia was to be found in the 
gardens ; the consequence was that each tree appeared 
fairly clothed with leaves, and though still somewhat 
thin, a dark green colour had come over the mass of 
coffee. 
During April and May the formation of buds and 
leaves increased more rapidly in the growing weather ; 
for although still very hot, a series of showery and 
steamy periods alternated, and the trees formed foliage 
with corresponding activity. Up to this period — the end 
of May — no leaf could be said to be " diseased " to 
any extent, and, indeed, it was not common to meet 
with a disease-spot at all. 
It may be fairly stated, therefore, that during the 
period between January 1st and May 31st, the trees, 
after a short period of rest or exhaustion resulting 
from the late " attack of leaf disease," set to work 
vigorously to produce leaves, and that during the interval, 
at first slowly and then more rapidly, they succeeded 
so far as to produce five or six pahs of clean, healthy 
leaves along each free twig. From January 1st to May 
1st, these trees would certainly have been pronounced 
"free from disease" in any estate report. 
But, unfortunately, the very weather which promoted 
the growth of leaves during April, i. e., alternations of 
showery and hot periods, dewy mornings, &c, also 
enabled a few straggling spores* of Hemileia to germin- 
ate here and there on the leaves. Consequently, before 
the end of May a coiTesponding number of " disease - 
spots" had burst forth from the infected leaves, and 
the spores produced by these were being shaken off, and 
more or less shed on smTOunding leaves. During the 
first week in June a good many more spots, still isolated, 
had made their appearance, and what would probably 
be termed a "mild attack of leaf disease" was notice- 
able. 
Before following the course of events further, I would, 
at the risk of repetition, call attention to the conditions 
which are found to rule the propagation of the fungus, 
and compare the facts with what occurred here. During 
the hot dry weather of February and March, apart 
from the fact that very f e v leaves existed for the fungus 
to attack, the want of moisture was of course inimical 
to the development of any spores accidentally conveyed 
to the living leaves from the leaves lying on the ground, 
and the few odd spores left from the last attack on the 
end leaves no doubt remained dormant. In April, 
however, a single showery night and dewy morning, 
probably followed by a steamy close day, might be suffici- 
ent to enable the spores near the stomata to send 
their tubes into the leaf ; once inside, as we know, they 
are safe, and from what is taught by experiments, we 
should expect to see the " disease spots " fully developed 
within about three weeks. That this actually occurred 
is evident from the gradual increase of spots dining 
May ; each spot produced would then shed its spores 
around as the breeze shook the trees, and each spore 
washed to the underside of the leaf is capable of at 
once germinating, &c, as before. In this manner it is 
* These spores may have been blown on to the leaves 
from the leaves on the ground, or they may have per- 
sisted through the hot dry weather. 
