6 5 o THE TROPICAL AGRICULTURIST. Qanuary 2, 1882. 
with all that takes place, no machinery or time- 
con suming processes being adnrssible on estates. 
4th. Having decided that a powder which evolves 
a soluble gas meeting all the requirements is simplest, 
it becomes necessary to see exactly when the applica- 
tion should occur la my 3rd report are data on 
which this can be based, and we see that the re- 
agent should be on the leav< s when the spores begin 
to germinate. What does this mean ? Simply that 
the soluble chemical is to be active duriDg the very 
wet weither, and consequently that it becomes washed 
to the roots of the coffee tree. Doubly cautious, 
therefore, must we be of such bodies as carbolic 
acid and mineral poisons, since the continued applica- 
tion at sufficiently rapid intervals would be a great 
source of danger at the roots. I may point out that, 
from this point of view, it matters little whether 
carbolic acid is applied as ordinary carbolic powder 
mixed with caustic lime, or in the chemically feeble 
compounds such as "carbolate of lime" &c. 
5th. But the planter requires more thau the 
above : it is nut enough that he possesses the re- 
quisite chemical, and knows when to apply it. He 
also demands that a minimum of labour force shall 
be employed. I take it that, apart from other rea- 
sons, e.-tates will not supply the labour necessary to 
go over all the acres once a week or so (as would 
be necessary in the wet season); and it does not seem 
wise to ignore this practical difficulty. 
6th. But suppose the planting community to have 
overcome all the above difficulties : suppose that every 
estate has arranged for efficient and continuous ap- 
plication, at the proper times, of a suitable remedy, 
the danger of reinfection must still be guarded 
against ; for a very few spores from native villages, 
abandoned coffee estates, the leaves on the ground, 
and from the jnngle, may rapidly make things bad 
again, if no precautions are taken. It is quite cert- 
ain, therefore, th>it a successful fight can only be 
made if the sources of reinfeciion are removed : in 
any case, the trees must be sheltered, and the dis- 
eased leaves swept and destroyed. 
7th. And the coffee must also be cultivated : 
manuring and pruning must be carried on just as 
well I need not comment further on the reasons 
for the advice given : it is useless to ignore any of 
the facts before us. 
8th. I would now ask: is it not a wiser plan to 
turn our attention to the slower but surer method 
of protecting coffee as much as possible against infec- 
tion ? By carefully destroying all leaves and prunings 
a great deal may be done towards ridding the estate 
of what spores are then on it : by jealously pre- ' 
Serving what shelter there is, and by providing more 
where possible, much can be done towards keeping 
spores from without. 
Manuring must be properly carried on under any 
circumstances : the chief ends lo be attained in the 
present difficulty are that the manure shall not be 
most active just when the rains come on. It is im- 
possible ti give any general directions for the whole 
island : plan i era on the estates can alone judge of 
these matters, since they are ruled by many and 
varying circumstances. 
Pruning must also be conducted as carefully as 
ever ; or even more eo. And now let me make a 
few remarks < n the system often employed. It is 
not uncommon f' r estates on the Kandy side of 
Nuwara Eliya to manure in January (say) and prune 
about the same time : on other estates the pinning 
has been left until June, while others perform the 
operation in 1 lie interval. 
Tho<-e haves which are formed very <;arly, and have 
the dry sunny weather of January, February, and 
March to work in— i. e. to elaborate the sap, as they 
are i x posed to light and air— possess this great 
advantage : the air is too dry for the vigorous 
growth of Hemileia, and little or no "disease" appears. 
In May and June the fungus is begiunitig to attack 
the succulent leaves formed in the preceding few 
weeks, and about July they will become badly diseased 
to disseminate more spores. If the pruning has been 
delayed until June, however, large numbers of the 
incipient disease spots, with the mycelium, become 
removed before the latter has fruited : there can be 
little doubt that this occurred in the caee of the 
field mentioned by Mr. Talbot, and I would call the 
earnest attention of planters to the success of his 
experiment. In this connection planters require simply 
their own methods, suited in each case to the estate 
and climate ; but, understanding the phases of the 
" disease," a great deal may be done by having either 
fewer leaves in May and June (so that a smaller 
surface for infection is offered) or many hardened 
and old ones — not because they resist infection, 
but because they will have been on the branches long 
enough to have done good work for the tree during 
a period of immunity from disease. I strongly urge 
plant'-rs to use all their thoughts and efforts on this 
part of the subject; for the gradual reduction of Hemileia, 
by depriving it of its best food at critical moments ap- 
pears to me by no means a hopeless task. 
I hope I have succeeded in rendering clearer the im- 
portant points, aud, m conclusion, I would indicate what 
appear to be some of the chief sources of error on the 
part of those who misunderstand the true nature of "leaf- 
disease," and its relations to coffee, and Hrmikia. On 
the one hand, a confusion of ideas seems to exist 
with respect to the meanings of the terms employed, 
and, on the other, a difficulty in conceiving such large 
effects to be produced by such apparently email causes. 
" Leaf-disease " is too frequently confounded with 
the parasite (Hemileia) which causes it: a disease is 
an abnormal state or condition of the organism, and 
we are here concerned with a disease of the leaves, 
caused by the lavages of a fungus. 
" Predisposition to infection " implies that the tree 
must have undergone some profound internal change, 
before it could be attacked by the fungus : not only 
does no evidence exist to supportthis view, but healthy 
coffee is as easily infected as any other. 
The coffee-plant or tree is a complex organism, and 
has a life of its own — a life which consists of the sum- 
total of the lives of its cells, harmoniously working 
together Kill a few cells or leaves, and little harm 
is done to the leaf or tree, because so many more 
cells and leaves remain to carry on the work ; hut, 
if many cells and leaves be destroyed at' frequent 
intervals, the whole tree suffers. 
Hemileia thus injures the tree as a whole, by des- 
troying the tissues which prepare its organized food, 
robbing it of substance, and overthrowing the balance 
of its functions. Did this occur but once, the tree 
-would put out fresh leaves, rapidly form new food- 
materials out of the crude sap passing up from the 
roots &c. , and repair the damage done : the continued 
repetition of this damage, however, gives the tree 
too little time. New leaves must be formed ere much 
crop can be produced and supported, and if these also 
rapidly become destroyed, continual efforts to supply 
new foliage make up the major part of the tree's 
duty, and the tax of bearing much crop is too severe. 
The sap of the tree does not simply flow up and 
down in definite channels, as does the circulating blood 
in animals : nor may the sap of a tree be too 
closely compared with the blood of an animal. Much 
error arises from misconception on these points It is 
not by pouring poisonous matter into a circulating 
medium, nor is it by merely tapping and drawing off 
fluids from the tree, that Hemileia cloes so much in- 
jury : it is in breaking down the little cells which 
manufacture the essential food of the tree, and thus 
