440 



the guard-cells become brown-coloured, i. e. they die off. 

 Before thèse cells are quite dead, the hyphae do not 

 penetrate the leaf tissue; first they grow intercellularly 

 and not before a larger number of the surrounding cells 

 hâve been killed, do they establish themselves there in 

 •and fin them up. 



As a rule this process takes place very quickly, as 

 will be seen from the artiflcial inoculations which will be 

 described later on. This is also the cause, why it is rather 

 difficult to flnd an exemple of this stage of the disease. 



The nodules of hyphae giving the peculiar aspect to the 

 leaves, lay for the greater part over the stomata and 

 apparently the death of the leaf is caused by suffocation. 



It is a curions fact, that, while coffee-leaves hâve 

 stomata only on the underside, the epiderm on both 

 sides becomes brown before the interlaying parenchymatous 

 tissue. 



In Liberian coffee in the first stage rather small spots 

 develop, often along the margin, but also half way up 

 the leaf; and thèse slowly extend themselves, till the 

 whole leaf becomes withered. In Surinam coffee on the 

 contrary usually the middle part of the leaf withers trans- 

 versely immediately; then gradually the rem aining parts, 

 the apex and the basis, become brown. When the leaves 

 are totally or almost totally withered, the stalk breaks 

 quite near the node; at first I thought that the leafstalk 

 was attacked primarly and that this caused the shedding 

 of the leaves. Experiments showed this hypothesis to be 

 false; when one allows a coffee branch with leaves to 

 wither, they always fall in this manner. By microscopical 

 observation dead cells are found under the strands on the 

 stalks, but only superflcially and not in such quantities 

 that they do any damage. 



