The Wohurn Experiments on “ Potato Diseased 
773 
Plot A for EA.ELT application of the dressing (before disease appeared). 
„ B „ LATE „ „ (on appearance of disease). 
„ C to be left untreated. 
The quarter-acre plots were subdivided, and while on one-half the ordi- 
nary bouillie bordelaise was to be applied, the other half was to be 
dressed with the bouiUie bordelaise sucree, the C plots in either case re- 
maining undressed. The plots of the first lialf (ordinary bouillie) will, 
for convenience, bo design.ated plots Aa, Ba, Ca. 
(6) Experiment on Special Varieties.- — Smaller plots of 
each were set apart for trials with nine different varieties of potato 
which Avere believed to be specially liable to disease. Three plots, 
as before — one for early, one for late application of the dressing, and 
a third to be left untreated, — were marked out, the dressing con- 
sisting of the bouillie bordelaise sucree. 
The varieties selected were the folloAving : — 
Early kinds— “ Myatt’s Ashleaf,” “ Early Puritan,” “ Early Rose.” 
Medium kinds — “ Dalmahoy,” “ White Elephant,” “ Reading Giant.” 
Late kinds—" Imperator,” “ Schoolmaster,” “ Victoria.” 
The varieties chosen for the “ steeping ” experiment Avith sul- 
phate of copper Avere “Early Shaw” and “Village Blacksmith,” 
and the same varieties also for the experiment with steeping in the 
sulphate of ammonia and nitrate of potash mixture. Each plot was 
•jV acre in size. 
Preparation of the Bouillie Bordelaise Mixtures. — In the prepara- 
tion of the bouillie bordelaise sucree certain precautions had to be 
observed, these being set out in M. Perret’s recipe for making it. 
The molasses must first be mixed Avith Avater, and the freshly slaked 
lime and Avater be added to it Avith constant stirring. Tlie sulphate 
of copper solution must be separately prepared, and then be added 
to tlie lime and sugar mixture, the AV'hole being kept vigorously 
stirred. A decomposition then sets in, resulting in the sucrate of 
lime (formed by the bringing together of the sugar and the lime) 
changing into sulphate of lime, and the sulphate of copper into 
sucrate of copper. An intense blue colour is thus obtained, and 
the mixture settles doAvn into a Avhitish-blue deposit which contains 
all the copper, and a clear liquid above. If the molasses be added 
first to the copper solution and the lime be added afterwards, a re- 
duction of the copper sulphate occurs, resulting in the formation of 
a suboxide of copper, the mixture acquiring a yelloAv and finally a 
red colour. 
The bouillie bordelanse sucrde should be always used Avhen freshly 
prepared, as, after standing for some time, it is apt to turn to a dirty- 
green colour, owing to slight reduction taking place. 
It may be Avell to note here that the vessels employed in making 
either of the bouillie mixtures should be of wood and not of metal, 
as the latter would be quickly eaten into holes by the mixture, the 
composition of which Avould become modified. At Woburn two 
wooden tubs holding 10 or 12 gallons each Avere found very suitable 
