The Wobur/i Experiments on “ Potato Disease” 779 
of the Society that it would most probably result in destroying the 
vitality of the tubers, but the trial was made in consequence of a 
suggestion that if steeping seed-wheat in sulphate of copper pre- 
vented “smut,” the disease in the potato crop might be similarly 
prevented. But the two cases are by no means analogous, for, with 
the wheat, the fungus is associated with unhealthy seed and is on 
the exterior of the seed, subsequently penetrating into it ; whereas the 
fungus of potato disease arises from sources external to the plant and 
may be carried to the leaves of perfectly healthy plants. Again, while 
the germ of the wheat is protected by the hard casing of the seed, 
the potato tuber has only a delicate skin which is not sufficient 
to prevent the known destructive action possessed by a solution of 
sulphate of coi^per. 
The steeping in a solution of sulphate of ammonia and nitrate 
of potash similarly destroyed the vitality, and fell very far short of 
producing the stated 42 tons per acre ! 
In connection with these steeping experiments it is well to men- 
tion that ill a trial on potatoes carried out at Lord Egerton of 
Tatton’s Home Farm, these two same methods were employed, and 
with precisely similar results to those obtained at Woburn. 
The Results. — It now remains to discuss the results of the 
weighings, with a view to ascertaining the following principal 
points : — 
1. Whether the application of the bouillie liad a preventive effect. 
2. Whether the application had a curative effect when disease 
had once appeared. 
3. Whether the mixture with sugar or that without sugar was the 
more effectual. 
4. Whether the application of the dressings had any influence in 
increasing or diminishing the produce. 
5. Whether, on the whole, it paid to use either dressing. 
It is advisable to consider the cases in which no disease whatever 
occurred separately from the others. These cases include all the 
“ early ” varieties and one “ medium ” variety (“ Dalmahoy ”). In 
these the influence of the dressings in preventing or checking 
disease is of course not apparent, and, generally speaking, it may 
be said of ‘ ‘ early ” potatoes that they are, as a rule, out of the 
ground before disease appears. It remains only, therefore, to 
follow the influence on the yield. 
Series 1. “ Beauty of Hebron.” — It is very clear from the figures 
that the part of the field where the plots 1 A, 1 B dressed with 
the bouillie bordelaise sucree occurred (for they were together at 
one end and the comparative ones dressed with the ordinary bouillie 
without sugar were at the other end) is poorer than the end where 
plots 1 Aa, 1 Ba were. The addition of sugar to the mixture showed 
no gain as compared with its omission. The dressing in each case 
showed a decrease of crop, the greater decrease being when the 
early application was used. 
Series 4. “ Myatt’s Ashleaf.” — A gain of crop was obtained by 
