268 FHE: ORCHID REVIEW. [SEPTEMBER, IQI2. 
00d work as a pathologist, and he reported that the mischief was caused 
by a parasitic fungus. This fungus passes into the intercellular spaces of 
the leaves by way of the stomata, and uses up the protoplasm. It then 
turns to the process of reproduction, and throws out spore-bearing threads 
through the stomata, and the green colouring matter then disappears in a 
circular patch, which ultimately becomes black. The grower now sees 
that something is wrong, and if an examination is made with a low-power 
microscope the little propagating bodies can be seen at the end of small 
branchlets. It is at this stage that the disease is most infectious, and these 
minute bodies are easily conveyed from leaf to leaf, where they germinate 
and form new centres of infection. 
In 1908 I was working in the collection at Leyswood, Groombrid ge, 
Sussex, and suddenly nearly every plant in two medium-sized houses was 
attacked, and the disease soon showed the amount of damage it was 
capable of doing by the quantity of leaves that went off in the fortnight or 
so which it took to cope with it. During this time drastic measures were 
taken ; the leaves were well sponged, and the very bad cut offand burnt ; the 
pots, stages, walls, &c., were well scrubbed, and the latter lime-washed ; 
the houses were also damped periodically with strong soot water, and the 
plants sprayed with weak soot water about twice a week. By these 
diligent and strenuous methods the pest was kept in hand and eventually 
eradicated. 
Since then I have had some experience with the same thing at Kew, 
and, with the help of a friendly amateur grower, have conducted some 
experiments on plants attacked by the same fungus in his collection. The 
first was to ascertain whether it could be made to thrive on plants of any 
other genus of Orchids, the testing plants being Oncidium macranthum, 
O. serratum, and Ada aurantiaca, but on none of them did the disease make 
its appearance. By the same method it was easy to get leaves infected on 
any of the Odontoglossums of the crispum set that were used. It also - 
seems partial to Odontiodas, which, of course, are half derived from 
Odontoglossum. The disease appears to be confined to the older leaves. 
Kew. ; CYRIL WARREN. 
This disease was first observed in 1892 on the leaves of Odontoglossum 
crispum growing at Versailles. Infected leaves were sent by M. Ed. 
André, Editor of the Revue Horticole, to the Laboratory of Plant Pathology 
at Paris, and in the following year a report by MM. Prillieux and 
Delacroix was published in the Bulletin de la Société Mycologique de France, 
stating that the disease was caused by a new fungus, Cercospora Odonto- 
glossi, which was then described and figured (1893, p. 270, t. 13, fig. 2). The 
disease was doubtless introduced from Colombia with Odontoglossum 
