Curative 
manures, 
Quicklime and 
sulphur. 
Tron sulphate. 
16 
water, or a solution of one-tenth per cent. is sufficiently strong to kill 
the spores of the fungus. Again, if the seed is considered to convey the 
infection, they may be soaked in a solution of the same strength. This 
will effectually kill all the spores of the fungus, and leave the seed 
entirely uninjured 
iii. In looking for some curative means by which it may be possible 
to rid the onion crop of the disease, the value of the knowledge of the 
life-history of the fungus me the disease becomes a parent. For’ 
the question now arises, at what stage in the life-history = the fungus 
should we apply such chemical remedies as we may have at our 
disposal. 
Wel have seen that the fungus in its mature condition is E 
in intimate connexion with the tissue of the onion leaf. The ot-like 
tissue, and the greater part of the fungus spends the whole of its life 
inside the leaf. It is “ae sg not advisable to attempt to kill the 
fungus at this stage, since any chemicals which would act upon the 
a 
are outside the tissue, and have not entered into any close relation pilin 
the plant. Furthermore, the first outgrowths from the spores are 
delicate and more easily acted upon by chemicals than the older parts sof 
the fungus, so that when a patak of onions shows signs of the presence 
of the disease the remedies should be at once applied, not so much wit 
the hope of destroying the mature fungus already there, but with a view 
of destroying the spores which it bears while they are germinating, and 
thus arresting the progress of the disease both in the affected plants and 
also from them to others. 
The first of the chemical remedies which may be applied to the 
diseased plants with considerable prospect of success is a mixture of 
E burnt quicklime and sulphur. 
can be no difficulty in obtaining plenty of quicklime in 
Seats and for this papa it must always be used when freshly 
burnt as quicklime loses its caustic properties and undergoes chemical 
change when kept any length of time. After burning it should be 
crushed to a powder and mixed with powdered sulphur in the proportion 
of two parts of quicklime to one part of sulphur. 
This mixture may be sprinkled on the diseased plants by hand o 
more effectively by means oe bellows, such as the Kentish hop- goi 
use for sulphuring t 
The mixture should be ‘applied — the dew is off the plants or 
after rain whilst the plant i is still w 
The chemical interaction which is perce by the mixture of sulphur 
and freshly-burnt quicklime leads to the formation of sulphurous acid 
and other allied gases. The gases are evolved slowly, and being readily 
diffusible they soon spread over the plant, and being easily soluble in 
water they dissolve in any moisture in the 1 c. The solution 
ill 
the chief use of sulphate of lime isa valuable manure, especially in 
Bermuda, where the amount of reo ah in the soil is very slight. 
A second chemical remedy which may be used for the onion disease 
is iron sulphate (F,SO,), and zine has the advantage of being 
readily wees in water, and hence can be applied in the liquid ae 
When a weak solution the iron sulphate will kill the fungus 
