THE CONTROL OF PLANT DISEASES DUE TO FUNGI. 23 
agricultural expert attributed his failure to spraying somewhat late in 
the season. According to him, the spray was not applied in time to 
prevent the fungus passing down the haulm. The farmer was con- 
vinced that spraying was useless to prevent disease, and in this case 
he was right, for no Phytophthora had appeared in the foliage of the 
sprayed plants and none was observed in the foliage of the unsprayed 
rows ; the infection came from the soil, but whence it came and how 
it reached the soil we do not know. None of these things had been 
anticipated or considered at all. Much labour could be saved in 
experimental spraying against mildew, whether using a fluid or a 
powder, by a few hours' study of the effect of the remedy on the fungus 
in the open. Is the fungus killed ? If so, to what extent and by what 
strength and under what conditions ? It would not be surprising 
to find that some recorded successes were really due to physical 
influences — the epidemic may have received a natural check ; on 
the other hand, failure may be due, amongst other things, to using a 
spray at an unsuitable time, an experience more than once recorded 
in the Bulletins of various Experimental Stations in the United 
States. 
A great many compounds are noxious to cryptogamic life, of 
which some are noxious to all plant life in strengths suitable for use 
against Cryptogams ; in general many are of mediocre value and a 
few invaluable ; the latter we must harness to suit our needs. Copper 
sulphate and the polysulphides of potassium are amongst the few 
compounds that have proved of great value in the past, and it seems 
very probable that perseverance with these may produce better 
results than trials with other newer and perhaps relatively more 
expensive remedies. 
It needs little thought to decide on what lines improvements must 
trend. When the text-book formula for applying liver of sulphur is 
used, we have a watery liquid which possesses poor wetting power ; 
it either rolls off the leaves or collects in globules, often failing to 
reach or cover the mildew ; new mixtures can be devised and are in 
use at Wisley that confer the power of adhesion on the liver of sulphur 
fluid ; moreover, the strength of the chemical can be much reduced 
in these bouillies without sacrificing efficiency. 
The cost of the chemicals used in spraying the Roses at Wisley 
against mildew in 191 4 worked out at about four shillings a 
thousand Roses, of which 10 per cent, are climbers and ramblers ; 
the chief sprayings were made on August 4 and August 20 respectively, 
and a minor operation on August 12, and as a result two-thirds of the 
amount of mildew present was absolutely destroyed. If the old 
method had been adopted, using liver of sulphur as the sole ingredient 
dissolved in water, the cost would have been halved with the same 
expenditure of time and labour, but without attaining any definite 
result. In 1915, by modifying the composition of the mixture 
used in 1914 and by adopting a different plan of action, not only 
was the cost of the ingredients used reduced to about one shilling 
