The ‘Spot* Disease of Orchids 
BY 
GEORGE MASSEE, F.L.S., 
A Principal Assistant , Royal Herbarium , Kew. 
With Plate XV. 
HE disease known as ‘ spot,’ which appears under the 
X form of brown spots or blotches on the living leaves 
of orchids, is unfortunately too familiar to cultivators and 
admirers of these plants, and although the health of the plant 
is not materially affected, except when the spots are unusually 
numerous, nevertheless the unsightly blotches on the leaves 
detract greatly from a full appreciation of the beauty of 
orchids when in bloom. 
The disease first appears under the form of minute pale 
spots, one to two millimetres in diameter, on the upper surface 
of the leaf, which vary considerably in number and arrange- 
ment, being in some instances numerous and crowded, in 
others few in number and scattered. Every portion of the 
leaf is equally susceptible to the disease, and the fact that 
very young leaves of diseased plants frequently show 4 spot * 
has been considered by some as strong evidence in favour of 
the disease being due to some parasitic organism ; this, 
however, is not the true explanation, the disease proving 
conclusively to be of a non-parasitic nature, and with proper 
[Annals of Botany, Vol. IX. No. XXXV. September, 1895.] 
