THE COFFEE-LEAF DISEASE OF CEYLON. ' 123 
enemy, although there is nothing to the naked eye which 
reveals its presence. The extent to which this takes place 
maybe readily judged from the two figures in Plate XI; 
fig. 1 is a portion of the epidermis of a young branch, and 
fig. 2 is part of the under surface of a coffee leaf. Accord- 
ing to Mr. Abbay there is a mode of propagation in this 
stage by conidia which are produced during the wet weather 
which is so favorable to the progress of the mycelial filaments. 
These conidia are developed at the ends of the branches 
of the mycelium in the form of radiating necklace-like 
strings of minute spherical bodies, the whole arrangement 
closely resembling the fructification of an Aspergillus, 
Whether these conidia are really part of the life-cycle of 
Hemileia must still be regarded with some doubt, inasmuch 
as fungus-cultivations are peculiarly liable to error from the 
introduction and development of the spores of other species 
than that which is the object of study. 
Mr. Morris finds that during the four or five months pre- 
ceding what the planters recognise as an attack of leaf 
disease,” and which is, in reality, nothing more than the 
period in the life-history of the Hemileia when the sporangia 
are developed, nearly every part of the coffee tree is invaded 
by mycelial threads. The absence, at the end of this period, 
of any empty sporangia leads him to think that the mycelium 
has travelled from some distance to finally invade the young 
foliage. If these were infected by sporangia blown on to 
them by the wind there would be some indication of their 
presence ; none, however, are found, and it may be concluded, 
therefore, that the mycelium has travelled to them from the 
stem and branches, or even from the ground. As this 
amount of growth could not be sustained by the small quan- 
tity of nutrient material contained in an individual sporadium, 
it must be concluded that the mycelium feeds in its course 
upon the organic matter dissolved in the moisture which, 
during the wet season, copiously bedeWs the sufaces over 
which the mycelium passes. 
As long as the mycelium is external to the coffee plant it 
apparently does it no harm, however copiously it ramifies 
upon its surface. But having reached the young foliage 
during the moist season the filaments begin to invade 
their internal tissues, and, in fact, to commence the 
ravages which are so injurious to the health of the coffee 
tree. 
The stomata of the leaves are closely set, and the mycelium 
is no less closely woven into an interlacing web. Sooner or 
later; therefore; a filament finds its way into a stoma, or, 
