THE COFFEE-LEAF DISEASE OF CEYLON, 121 
in size, but always preserve a circular outline, except where, 
as occasionally happens, the accidental coalescence of two 
patches produces one of irregular form (PL IX, hg. 2, a). 
They are most numerous towards the apex of the leaf, the 
tissue there being somewhat younger and more succulent, 
and therefore more easily attacked. The centrifugal deve- 
lopment of the patches is sometimes arrested by the barrier 
presented by the midrib or a vein, but this is not always the 
case (PL IX, fig. 1, a). 
When a diseased patch is examined with a low power it is 
seen to be covered with the somewhat symmetrically disposed 
clusters and sporangia, the most mature being in the centre 
(PL IX, fig. 4). Further examination shows that these 
clusters occupy stomata, PL IX, fig. 5 ; and fig. 6 shows a 
cluster in which some of the uppermost sporangia have 
fallen off, allowing the oblique attachment of the rest to the 
mycelial threads which fill up the openings of the stomata 
to be seen. Mr. Morris describes the fully ripe and detached 
sporangium as an ovate, oblong, or reniform body, covered 
externally on all sides but one with globose or wart-like 
papillae. The smooth surface of the sporangium is under- 
neath on the side of attachment, and the fact that on all 
other sides the sporangium is covered by wart-like papillae 
gives it a peculiar character, which, according to Mr. Berke- 
ley, is found in only one other fungus, viz. in Badhamia.^* 
The immature sporangia are destitute of papillae. 
The Hemileiai^ itself not without its enemies. In PL IX, 
fig. 1 A, a dark-coloured patch is shown where the sporangia 
have been attacked by some other fungus, possibly an Asper- 
gillus. In fig. 3 the sporangia are colourless towards the 
centre of the spot, their contents having been destroyed by 
some other agency of the same kind; in this patch also is 
represented the larva of a small undescribed dipterous insect 
(fig. 7), which likewise feeds on the ripe sporangia. This 
larva was first noticed in 1874 ; Dr. Thwaites then remarked : 
‘‘ Sometimes these little maggots are very numerous, and it 
could be wished they were still more so, and that thus the 
fungus spores might be altogether consumed and the pro- 
pagation of this terrible pest arrested.^’ 
If a vertical section be made through one of the diseased 
patches of a coffee-leaf the connection of the mycelium with 
the masses of sporangia can be traced and the destructive 
eflect of the former upon the leaf tissue readily studied. The 
bundle of mycelial filaments, to each of which a sporangium 
is attached externally, forms a felted mass, like a plug, which 
fills up the cavity, into which a stoma opens above. This 
