February i, 1882.] THE TROPICAL AGRICULTURIST. 
717 
COFFEE LEAF DISEASE: THEORETICAL IN- 
VESTIGATION, AND PRACTICAL EXPERIMENTS 
IN CHECKING ITS RAVAGES. 
Wo can do little i v today Hum call attention to 
tho two important communications on the subject of 
Hemilcia vastatrix which will be found elsewhere. Mr. 
Stephen Wilson has brought to his investigation of our 
coffee-leaf fungus considerable experience and acknowledged 
ability displayed in pursuing a very similar enquiry into 
three of the great enemies of British agriculturists, 
namely, club-root in turnips, rust in wheat, and tho 
potato disease. He has interested himself in our local 
pest purely as a scientist accustomed to investigate fungoid 
life, and tho very modest relation of tho result of his 
study of tho " loaf-disoaso literature" and of the ex- 
amination of the loaves and spores sent to him from 
Ceylon cannot fail to be interesting. It will bo observed 
that Mr. Wilson has felt himself justified in applying 
to " this most important fungus " what lie believes to 
bo " tho true life theory of a great many fungi which 
become parasitic in tho tissues of higher plants." At 
the samo time, ho guards himself against being supposed 
to have made a comploto substantive investigation of 
the ooftoe fungus, sooing that he has had no access to 
the living plants, and ho refers to the labours of Messrs. 
Abbay, Morris and Ward as rendering such an investig- 
ation unnecessary on his part. ■'Side-lights" have been 
all Mr. Wilson hoped to cast on tho coffee pest, and 
yet it seems to us, as non-scientists, that this gentleman's 
theory of " Apogestation " affects very materially the 
lifo history as finally laid down by Mr. Ward. It would 
seem, for instance, as if Mr. Wilson afforded tho ex- 
planation of the experience of Captain Bayley at Monrovia, 
Gallo, where the existence of tho disease was apparent 
on his young coffee (from imported seed) almost before 
a pair of fully-formed leaves were developed. The practical 
lesson, however, that Mr. Wilson would wish to convey 
is the uselossnoss of protecting tho full-grown leaves 
from the disoase-sporos " atmospherically conveyed " when 
the germs of the fungus arc already within such loaves 
from their wry earliest stages. Nevertheless tho practical 
valuo of endeavouring to starve or to prevent tho germ- 
ination of tho pest is fully acknowledged. We regret 
thai \w cannot reproduce tho tracing of the various 
stages of tho fungus sent us hy Mr. Wilson: to attempt 
to lithograph the ligures with the means at our command 
locally, would, wo fear, only afford a misleading represent- 
ation ; but we shall be glad to show tho tracing to any 
one Interested. Mr. Wilson endeavours to represent in 
it the life-cycle of Uemileia divided into its parasitic 
and nun parasitic systems. .Mr. Ward's liual Report only 
reached Mr. Wilson after he had written his letter; 
but our "Aberdeen Correspondent" enables us to infer 
that his opinion is not specially ull'ectcd thereby. Our 
correspondent writes: — 
"Mr. Wilson's letter anticipates the publication of 
thii laper on 1'otito hiseaso hi, n >t. uad_\ y.-t but 
will Imvi to be iii print before tliu Observer with the 
letter 000168 to this country. It is to bo sent to the 
London Tiiiif* 'it they will accept of it;' ho will likely 
bo bagged by your London correspondent for you. 
'■ I sent Mr. Wilson Mr. Ward's Report, nnd two days 
Inter I had a mile mid a ball's walk with him. I told bill] 
you wanted bis opinion on it. Eleaaid 1 It would hardly 
do to criticize another nan's work. I might being a uvst 
of hornets about my ears.' I asked 'Is there anything in 
it that affects your theory?' and 'Was there any- 
thing in your letter you would not have said, had you 
read Mr. ward's Report before writing?" Ans., 'Nothing 
but what can be explained, and I would not have said 
' where does the first spore of the season come from ? 
as I see he accounts for that as coming from diseased 
leaves on the ground. 
" In course of our talk ho said : ' It is an assump- 
tion to say the mycelium enture the stoma, as no micro- 
scope can show it doing this. Tho leaf being opaque, 
a high power prevents this beuig seen, and with a low 
power you eannot see the mycelium at all. 
" Damp and steamy atmosphere promotes fructific- 
ation of Hemekia. Mr. Ward treated a leaf or leaves 
to steamy atmosphere in a wardian case pins a sowing 
of spores, and, on seeing disease fruit, concluded his 
spores dit it. To have made his proof absoluto be would 
have to treat a leaf of the samo plant to tho steam- 
ing atmosphere of the wardian case minus he spoors 
and noted results. 
"If tho Planters' Association woidd minute thanks 
to Mr. Wilson, and send him a copy of the minute, 
I am certain ho would bo gratified. It might stimul- 
ate him to undertake experiments of a cultivate kind. 
Unfortunately he is nothing of a chemist, but accurate 
microscope examination may bo more essential for such 
experiments than knowledge of chemicals. Of course, 
ho has not coffeo to experiment on, but he might try 
something on potatoes. " 
A vote of thanks formally conveyed would, indeed, be 
an easy way of acknowledging Mr. Wilson's services 
and of stimulating him to further investigation : we 
commend the suggestion to the Committee of the Planters' 
Association. 
But we may now turn from Mr. Wilson's scientific 
investigation and interesting theory of apogestation, to 
tho paper in winch Mr. Schrottky is understood to 
sum up finally the results of his experiments in checking 
and eradicating the disease on a plantation in the 
Dumbara Valley. Since April last year, a fair trial 
has boen given to the treatment with carbolizcd powder 
on Gangapitiya, the estate in question, and with the 
reports beforo us dating up to the 2nd instant it is 
difficult to see how the valuo of the application can 
be denied. We learn that, with the exception of Ganga- 
pitiya, not an cstato in Dumbara is at present escaping 
one of tho worst outbursts of the fungus that has been 
witnessed for some time back. Why should this estate 
bo comparatively exempt ? There is nothing in its con- 
ditions of soil, age of coffee, or surroundings, to ex- 
plain the difference, and assuredly there is no evidence 
after nearly nine mouths' experience of tho carbolizcd 
powder doing harm to the roots of the coffee trees. 
On the contrary, tho cofloo is described as luxnriaut 
and in splendid condition, as compared with neighbouring 
estates, for the blossom which is now appearing. No- 
thing succeeds like success, and of course the plan tun* 
will be glad to welcome satisfactory practical results 
more than tho most interesting scientific theory. If 
Gangapitiya fulfils \\< present promise an. I passes through 
the blossoming season satisfactorily, we may be sure 
that on a good many more properties the application 
of corbolizod powder u ill receive a hystenmtie trial. March 
and April, Mr. Schrottky telLs us, are the Ih'M months 
to begin, and a supph of the material must Ih' provided 
in time. Gangapitiya therefore should bo once more 
MM ted about the in. I of this month by lvpre.x'Utrtti\c» 
