46 MR. G. MASSEE ON THE DISEASE 
Remedial measures of a practical character require to be 
adopted, and these have been recommended to the Government 
of Jamaica, by whom the specimens examined by Mr. Massee 
were sent to Kew for Report; but, after all, remedial measures 
alone cannot be depended upon to eradicate a disease of this 
character. Experience has shown that the disease must, in the 
first place, be restricted within the narrowest possible limits ; 
and, in the second place, all badly affected plants should be 
wholly destroyed. D. Morris. 
Report oN THE DISEASE OF “ Cocors” (CorocastA) 
IN JAMAICA. 
The disease is due to the presence of a fungus belonging to 
the genus Peronospora. 
In the incipient stage, a “tuber” or “head” presents, on 
transverse section, a number of minute bright yellow spots 
scattered over its substance, which, at a later period, become 
brown or blackish, and the intermediate portion tinged brown ; 
eventually the whole tuber, with the exception of a peripheral 
portion about two lines wide, becomes blackish and decayed, 
but, so far as we are able to judge from the specimens submitted, 
remains comparatively dry, and not putrid as in the potato 
disease, due to the attacks of a fungus belonging to the same 
genus. 
The yellow spots correspond to the vascular bundles, which 
are always attacked first, the mycelium spreading through the 
entire substance of the tuber along the cavities of the tracheids, 
from which it passes to the adjoining parenchyma. The colour 
is due to the disintegration of cellulose; and the tracheids are 
frequently ruptured at an early stage owin g to excessive develop- 
ment of hyphe within them. 
The two forms of reproductive bodies, conidia and resting- 
spores, were met with: the first are only produced on hyphe 
exposed to the air, or in internal cavities; the latter on threads 
in the substance of the tuber. 
The disease is stated to be confined to the tubers, or at all 
events to show itself there first, and in all the specimens seen it 
is perfectly certain that an entrance has been effected at a point 
where the skin had been broken—in one example, where an off- 
