964 
THE TROPICAL 
AGRICULTURIST. 
[May if i88z 
To the Editor of the Ceylon Observer. 
COFFEE CULTIVATION AND LEAF DISEASE, 
BY A MYSORE PLANTER. 
Dear Sir, — As one who has for many years devoted 
attention to the cultivation of coffee, I feel you will 
most obligingly permit me tojoin in the renewed friendly 
controversy about leaf-disease and to offer a few more 
remi.rks in support of my long-cherished opinion both 
as to the existence of special predisposing causes for 
the attacks of fungoid parasites and as to there being 
ways and means of raising trees from well-prepared and 
carefully-selected seed of hardy varieties, which will 
at any rate to a certain appreciable extent, have dis- 
ease-resisting powers. 
Having maintained in all my essays and letters 
during tbe last six years that constitutional debility, 
either hereditary or acquired, renders the plant more 
liable to disease, and that this susceptibility increases 
in a corresponding ratio to the persistence with which 
we continue either to propagate from a deteriorated 
stock or maintain a system of imperfect cultivation of 
the soil, or neglect to supply those constituents which 
frequent crops of coffee are known to remove from the 
land, I do not desire to escape from a just share of 
any censure which I may deserve for continuing to 
believe that all remedies must go into and affect the 
soil so as to strengthen and invigorate the constitution 
of the plants. 
As you are aware, I have advanced a theory that 
Hemileia Vastatrix finds the best conditions for its de- 
velopment during the abnormal continuance of an 
otherwise transitory condition of the starchy and 
sugary constituents of the cell-sap, and I have ventured 
to assert on the authority of certain humble attempts 
at experimental observation, that a want of alkalies and 
phosphates in an available form, at certain seasons of 
the year in a soil in defective mechanical condition, 
is at' least one of the principal causes of our troubles. 
As fungi without exception present the p< culiarity 
of never forming starch (Sack) 1 have concluded that 
it is probable fungoid parasites obtain their food in 
the most suitable form from such hosts as are tempor- 
arily (if I may be permitted the expression) either of 
a lymphatic temperament, or are unable to obtain a sup- 
ply of some starninal principles in sufficient abundance 
for their requirements. 
I am fat from believing that our soils are suffering 
from absolute exhaustion, but I venture to think that 
each variety of plant of the same species undoubtedly 
possesses different powers of collecting from tbe land, 
an adequate supply of inorg nic'plant-food necessary 
to maintain certain obscure functions in healthy ac- 
tivity. \Ve know that healthy plants contain more 
alkalies than weak ones (Harman) and agricultural 
chemistry clearly points out that it is rather I he con- 
dition than the quantity of the elements of plant- 
food which influences fertility. 
I have carefully perused tne able and elaborate re- 
port of the Government Cryptogamist, together with 
the interesting explanatory letter which appeared in 
your issue of the 13th December, and I feel that every 
planter is placed under the deepest obligations for the 
untiring zeal and ability which has been brought to 
bear on the investigation of the scourge, and for the 
courteous manner in which the arguments aud suggest- 
ions of others, who have interested themselves in the 
mat'er, arc dealt with. 
Taking advantage of the encouragement offered, I 
am induced, although with the greatest diffidence, to 
venture a few remarks on certain points touched upon, 
in the explanatory letter above referred to, which 
having appeared in your columns, I presume may be 
considered debatable : — 
" It should be remembered that the crop obtains its 
principal nutriment from the leaves just as does the 
fungus and unfortunately both take similar materials." 
A most important consideration is involved iu this 
observation. Although the plant and the fungus may 
require similar food-materials for tbeir principal nutri- 
ment, still surely each can only utilize them under 
special favoring conditions. If this is not the case, 
there can be no further use for studying physiology. 
The planters' prospects are indeed poor, if the only 
requirements of the fungus are a supply of healthy 
coffee cell-sap and little moisture. 
Why was this not the case before ? 
We know that the ash of the coffee bean contains 
potash, lime, and magnesia, together with phosphoric 
and sulphuric acid, and we are taught that these 
constituents are required for certain physiological 
purposes in the economy of plant-life, and, although 
it were impossible to gain accurate information re- 
garding the likes and dislikes of Hemi da, I entirely 
fail to comprehend why the investigation connected 
with the nutrition of plant-cells, even though it should 
require the " appliances only to be found in the 
well-equipped laboratories of Europe,'-' should be for 
an instant considered as unworthy of peculiar atten- 
tion, when making further research relative to tbe 
pest under notice. 
The following extracts from Sach's Text-book on 
Botany explain what 1 mean : — 
" The combinations of food-materials must be sub- 
ject within the tissues to progressire changes of posi- 
tion in addition to and in consequence of their chemi- 
cal transformations." — " The nutrition and growth of 
all plants hitherto examined for this purpose is impos- 
sible or abnormal if any of these elements are want- 
ing." — "The constant occurrence of compounds of 
phosphoric acid in company with albuminoids as well 
as of potassium salts in organs containing search and 
sugar, points towards definite relations which tbey may 
possess to those chemical processes that immediately 
precede the processes of construction in plants. 
" Nobbe has recently shown that if plant- materials, 
otherwise complete, but possessing no potassium, 
are supplied to plants (as buckwheat) they behave 
as if they were absorbing only pure water instead of 
a solution of food-material. They do not assimilate 
and show no increase in weight because no starch can 
be found in the grains of chlorophyll without the 
assistance of potassium." 
Professor Wortbington Smith on Peronospera In- 
festans says : — " I have got my most abundant 
materials from the tuber when soft and almost trans- 
parent like painters' size ; in this state the starch is 
utterly destroyed and what is more curious there is 
no offensive smell. The tuber frequently decomposes 
with a horrible f 03 tor and turns whitish inside ; the 
starch is then all present and not much injured and 
very little indeed can be seen of the fungus." 
" Predisposition to infection implies that the tree 
must have undergone some profound in ernal change 
before it could be attacked * * * Healthy coffee is as 
easily infected as any other." 
The analogy which exists between the life of a 
plant and that of a human being must of course be 
treated with caution ; but is nevertheless useful for 
explanatory purposes. The various works I have con- 
sulted lead me (however erroneously) to believe that 
the word predisposition as generally understood does 
not imply the absolute necessity for any such extreme 
condition ; but may simply mean either an acquired 
or hereditary fitness, liability or adaptation to adinit 
of any change, affection or influence under certain favor- 
ing conditions, which, under ordinary circumstances, 
would have been insufficient to admit of a similar 
