SUB-IRRIGATION FOR LETTUCE. . 75 
alternate the plots. This, however, cannot be extended 
very far, as the difference in heat in the two ends of a house 
is considerable. <A very’ good plan is to take a section of a 
bed in the middle of a house and treat by one method of 
watering, while two sections of the same size on either side 
are treated according to the other method. This has been 
done in several cases, and some examples are given in the 
third table. In these experiments, the plants were treated 
in the same manner as those in the experiments above men- 
tioned, z. é., all were sub-irrigated until they were planted 
in the benches. After that time sections A and C were sub- 
irrigated, and section B was surface-watered. The average 
gain of the sub-irrigated plots over the surface-watered was 
about 38 per cent, or very nearly the same as the average 
of the 15 experiments in the second table.— 
COMPARISON OF SURFACE-WATERED SECTIONS WITH SUB- 
IRRIGATED SECTIONS ON EITHER SIDE, 75 GRAND 
RAPIDS PLANTS IN EACH SECTION. 
Section A, sub- | Section B, sur-| Section C, sub- 
irrigated. face- watered. irrigated. 
Experiment I. .| Weight, 385 ozs. | Weight, 325 ozs, | Weight, 420 ozs. 
Experiment II. . 55 487 ‘‘ ss 329 ‘* * 496 ‘ 
Experiment III. . - go8 a 229 ‘ pe me oh 
“Tn all of the experiments thus far referred to, but 
one point has been considered, and that is the increase in 
weight by sub-irrigation. Aside from the relative preva- 
lency of disease in plants treated by the two methods, there 
are but few practical questions. 
‘* Although not a matter of much practical importance, 
some interest attaches to the fact that sub-irrigated lettuce 
is earlier than that grown in the ordinary manner. It does 
not really come to maturity any earlier if by that is meant 
the stage at which the plants cease to increase in weight, 
