546 
THE TROPICAL 
AGRICULTURIST. [December i, x88i 
Any one therefore, professing to have discovered 
a method or means by which the condition of the 
sap of the coffee tree can be rendered more or less 
unsuitable to the development of the fungus, should 
not be considered prima facie undeserving of en- 
couragement and of a careful trial of his method. 
10. The Oyptogamist then passes on to refer to 
the second set of my experiments based on what he 
is, pleased to term "sounder" principles. Asa mat- 
ter of fact there are no principles at all involved in 
these experiments. The fungus is external to a large 
extent, easily accessible, and it was merely a ques- 
tion of empiric trial to decide what substance or 
combination of substances would destroy it without 
affecting injuriously the coffee tree. 
Here, it may not be out of place to mention that 
the cryptogamist's prima facie rejection of metallic 
poisons as likely to be injurious to the roots of the 
trees is not justified, as the soil has a peculiar power 
of decomposing the same and thus rendering them 
insoluble and innocuous. I have only to point out 
that metallic poisons are constantly used for similar 
purposes with no ill effect to vegetation, singling out 
the successful battle with the Colorado beeile as an 
illustrative example. 
For the destruction of Hemileia I have selected 
on the basis of comparative trials with a great num- 
ber of suitable substances, (among which sulphur and 
lime,) carbolic acid as most suitable and efficient. 
The properties of carbolic acid, it seems necessary 
to reiterate, are two- fold. In its concentrated and 
uncombined form it is highly caustic and destroys 
organic compounds by breaking up their tissue ; but 
in certain combined forms or in a highly dilut- d 
state its causticity ceases and then its second pro- 
perty, that of a most powerful antiseptic even in most 
attenuated dilutions, comes alone into play. In its 
presence no fungoid forms of certain types can develop 
without more or l<-ss immediate collapse, and to this 
is due its great efficacy as a disinfectant which has 
deservedly raised it in the estimation of the public, 
above other disinfectants, such as sulphurous acid, 
permanganate of potash, sulphate of iron, chloride of 
lime, etc. In employing it against coffee leaf-disease 
1 have relied entirely on this second property ; by 
using it in a combined form, I have greatly reduced 
its causticity, and by binding it in the form of a 
dry powder have enabled the planter to further dilute 
it with anything suitable and to apply it in the form 
of dust to the trees. 
The powder is much lighter and can be applied in 
more perfect manner than the sulphur and lime mixture. 
11. At an early stage of my experiments I had 
published a description of the main composition of 
this powder. The Cryptogamist kindly corrects me 
and states : "an intimate mixture of fine clay powder 
containing 12 to 15 per cent, of carbolic acid is mixed 
with lime." 
I beg to hand you the following : — 
Colombo, 12th November 1881. 
E. C. Schrottky, Esq., Colo obo. 
Dear Sib, — in reply to your enquiries we beg to state 
that we have prepared the carbolized powder sent for 
use in your experiments against coffee leaf-disease on 
'Peradeniya,' ' Pallekelle,' 'Gleneagles,' ' Gangapitiya,' and 
other estates strictly in accordance with your instructions, 
and that the same would be wrongly described as a 
mixture of clay and carbolic acid, — no substances of the 
nature of clay entering into its preparation. — We are dear 
sirs, yours faithfully, Lewis Bkown & Co. 
It makes of course some difference whethere mare 
mechanical mixture of clay and carbolic acid or a 
chemical compound of the same is employed. 
12. You will find in enclosure my statements to 
the effect that the powder, as used by me, parts slowly 
with its carbolic acid in the form of vapour, that 
this said vapour is distinctly noticeable under ordinary 
circumstances for about 8 to 10 days after each applica- 
tion, that further, the powder touching by nature of 
its distribution the different external forms of the 
fungus either on the leaves or scattered elsewhere 
about the area, as well as the vapour given off by it, 
it will have a maximum effect when there are heavy 
dews or slight showers after the application to supply 
the moisture necessary for (absolute) contact, and that 
I advised not less than two applications following at 
an interval of ten days. 
The spores and other forms of the fungus would 
therefore be kept, by this said treatment, in an 
atmosphere tainted with carbolic acid for a minimum of 
twenty days; they would be subjected to the influence 
of condensed moisture, such as dew, or of showers of 
rain, thus enabling the powder to establish contact 
where it touches the spores etc. and likewise dissolv- 
ing the vaporized carbolic acid and making it effectual 
where the powder does not actually touch the fungus. 
13. Being fully aware of these statements on my 
part, the Cryptogamist n<>w describes in the paragraph 
under comment, an experiment setting forth that 
spores subjected to the action of an atmosphere con- 
taining vaporized carbolic acid for 24 hours had 
germinated and that therefore as with other reagen 
the germinal tubes will have to be attacked with a 
solution of the acid. This experiment has been wrongly 
quoted by the Cryptogamist and supplies no data, 
bearing in any way on the merits of the carbolic acid 
vaporization process, as recommended by me. 
The Cryptogamist omits to use the powder which I 
or others would have gladly supplied him with, he 
keeps the spores only for 24 hours in contact with 
a carbolized atmosphere, and he fails to supply tho- 
condensed moisture necessary for contact. 
14. I fail to reconcile some of the Cryptogamist's 
further statements regarding the action of the powder 
on the fungus. He says : "It is true that where 
water is in contact with the powder a solution is 
obtained sufficiently strong to kill germinal tubes, 
but the diffusion of this over the leaf is a very slow 
process " and then- further on — " but such a solution 
is not produced in the way described in the experi- 
ments at Gleneagles, Pallekelly, etc." 
It ought surely not be necessary for me to point 
out that nature is not sufficiently prejudiced to with- 
hold dew and rain, which the Cryptogamist consider*, 
affords sufficient moisture to form a solution in thejv 
case of the sulphur and lime treatment, so prominently 
brought forward by him. 
15. There remains now only for me to deal with 
the Cryptogamist's opinion "that more might be done- 
with some modification of the powder, if it were not 
for the fact that the accumulated powder and solution 
are a source of danger at the roots." This is illustrated 
by an experiment, shewing that a mixture of carbolio- 
acid powder and lime was sprinkled round the trees, 
then watered for three weeks and that the results 
were disastrous to the trees. There are, however, no» 
details given as to whether the ordinary carbolio 
acid powder (which is a mixture of clay and aeid)s 
or the special prepared powder as used by me has 
been employed ; the age and condition of the treea 
are not given, nor the quantity of powder used per- 
tree, nor the amount of water per square foot which 
has been consumed in watering these ssid trees for 
three weeks. In the absence of these details I cannot 
further comment upon this experiment. 
Suffice it to say that my experiments either OB 
small or large areas have yielded sufficient evidence 
to enable me to state that there is neither now nor 
has there been at any previous stage the slightest 
reason to think that the carbolized powder in the way 
and manner in which its use has been recommended 
by me, has affected or is likely to affect the trees 
injuriously through its being washed down to the roots,. 
