The Woburn Experiments on “ Potato Disease.” 
775 
wise the deposit would settle down at the bottom) and baled out 
into the spraying machine. The machine used was the “Eclair ” 
of M. Vermorel, sold by Messrs. Chas. Clarke & Co., Windsor 
Chambers, 33 Great St. Helens, London, E.C., the price of it being 
35s. complete. This machine was found to work very effectually. 
Mr. Elliott thinks that a better plan than baling out the 'mixture 
would be to have a large wooden tap at the bottom of the cask and 
to fill the “ Eclair” from it. He considers the work of applying the 
dressing rather heavy, the weight alone of the machine when full 
being considerable. A slight increase of the daily wage paid to the 
men was made, and this got over any difficulty. The man who 
applies the dressings should be provided with an old suit of clothes, 
as it is impossible to keep the spray away from the person using the 
machine. 
Particular instructions were given that the spraying should 
be done as thoroughly as possible on the under side of the leaf. 
As Mr. Carruthers, the Society’s Consulting Botanist, has pointed 
out, it is on the under side of the leaf that the potato is attacked 
by the spores of the fungus {Phytophthora hifestans) settling on it 
and forcing its roots or hyphce, as they are scientifically termed, 
into the stomata or openings which occur on the under side of the 
leaves, but far less numerously on the uoper surface. On the upper 
surface, moreover, the leaf is provided with closely-set palisade cells 
which resist the entry of the hyphce of the fungus, whereas these 
cells do not exist on the under side of the leaf. This view of the 
reasons that make it desirable to spray the under side especially is 
disputed by some practical men, including M. Vermorel himself, who 
maintains that effective spraying of the upper side of the leaves is 
ample, and that sufficient of the mixture finds its way below. But 
the botanical point involved is not questioned, and hence it seems 
sound reason and practice to guard the lower surface particularly, 
more especially as, in doing this, the operator cannot well fail to 
give a copious dressing to the upper surface at tlie same time. 
This, no doubt, involves the use of a larger quantity of the mixture, 
but it is the safer practice. With care it was found quite practi- 
cable to direct the nozzle of the machine under the leaves and, turn- 
ing it upwards, to spray the under side of the leaves effectually. 
Mr. Elliott found that when the tops of the plant were still 
small, one man working with an “ Eclair” could spray half an-acre 
of potatoes per day, but that when the tops became larger, not 
above one-third of an acre a day could be done, and that when the 
tops grew very large it was im 2 )Ossible to spray each plant effectually 
without using a great amount of the ch'essing, as much as 200 
gallons to the acre being occasionally required. It was found in 
■general that the quantity used varied from 100 gallons to 170 
gallons acre, according to the size of the tops. For a first 
dressing 100 gallons was enough, and for an average crop 120 
gallons per acre might be taken as a fair quantity. 
The weather best suited to the application was found to be a good 
VOL. III. T. S. — 12 3 G 
