270 - THE ORCHID REVIEW. 
A large healthy specimen of this remarkable Orchid stands at the south- 
west corner of the Victoria tank at Kew, whose behaviour in the near 
future will be watched with interest, as judging by appearances it is mature 
enough to flower at any time. A peculiarity of the species is well shown 
in this particular specimen, namely its curious habit of producing 
numerous erect branching roots round the base. Similar roots are 
produced by certain Catasetums, Gongoras, and some other Orchids, but 
their precise use to the plant has not been made out. 
R. A. ROLFE. 
CHEMICAL COMPOSITION OF CATTLEYA. 
WITH a view of ascertaining the cause of the degeneration observed in 
certain Orchids after a few years cultivation, and some means of preventing 
it, Mr. Smee has put together a few observations on the chemical com- 
position of Cattleya, together with some suggestions as to its food require- 
ments, and laid the same before the members of the Orchid Committee of 
the Royal Horticultural Society, by whom they were referred to the 
Scientific Committee. A copy of these papers has been kindly sent by 
Mr. Smee, which are too long to reproduce in full, but we make the 
following extracts, for the subject is one of the greatest interest to Orchid 
growers. 
In the Gardeners’ Chronicle of February, 1894, there was an article on 
the chemical composition of Cattleya labiata, also giving the analyses of 
rain-water in temperate and tropical climates, which showed a large in- 
crease in the amount of nitric acid in the rainfall of the tropics as compared 
with the temperate zones. This is as may be expected, for it is well known 
that thunder rain contains nitric acid, derived from the rapid oxidation of 
the nitrogen of the atmosphere by the electric discharge, combining 
immediately with the pure ammonia in the atmosphere, forming ammonia 
nitrate. 
In the neighbourhood of our large towns the atmosphere is injuriously 
affected by the products of the combustion of coal, in the form of sul- 
phurous and sulphuric acid and ammonia, and in some places—for instance, 
the Tyne and Clyde—by chlorine given off from the chemical works. 
There is also given off some of the more volatile petroleum oils, which form 
a greasy slime, which in fogs is deposited on the glass of our plant-houses, 
and falling upon the leaves of the plants, interferes with their power of 
osmosis and exosmosis so necessary for their well-being. 
I have myself noticed that the quantity of ammonia in the atmosphere 
was subject to considerable variation; the greatest amount was detected 
on days when the electric currents were feeble or totally absent. I have 
