1914) 
DUGGAR AND COOLEY—FILMS AND TRANSPIRATION 15 
fiim may actually effect à diminution in the rate of transpira- 
tion, although the transpiration data do not suffice to warrant 
more, at present, than an impression. In fact, the night 
“runs” should be considered apart from those of the day, for 
the latter are much more satisfactory. 
Experiments with potted plants.—The experiments with potted 
tomato plants were divided into two series which were consec- 
utive in time, and different only with respect to the substances 
applied to the leaves. Ав far as has been ascertained, this is 
the first time that tomato plants have been used in such work, 
but in our experience they are more satisfactory than potatoes. 
In the first series (table ш) 30 plants were used, іп lots of 
10 each, for the applications of (1) strong Bordeaux mixture, 
(2) weak Bordeaux, and (3) controls. In the second series 
(table rv, v) 80 plants were used in 8 lots, and the substances 
employed as sprays or dusts are noted in the tables. In the 
second series it is to be noted that there are 3 substances of 
the nature of films (Ca(OH)2, АКОН)з, and lime-sulphur), 1 
true suspension (clay), and 3 powders (charcoal, СаСОҙ, and 
powdered Al(OH)s). 
The methods of procedure involved in these experiments 
have already been outlined. It is necessary to add, however, 
that the plants used were about 12 inches high and as uniform 
in size as could be obtained. It was not possible satisfactorily 
to standardize plants for an experiment extending over several 
weeks: and it was necessary to rely in part upon numbers, 
and in part upon a rigidly accurate method of selecting the 
individual in each lot to eliminate any errors. Тһе method 
of selection consisted in getting together 8 plants so similar 
in size and vigor that no choice could be made between them, 
then distributing these at random to the 8 lots, this being 
continued until each lot embraced 10 plants. 
In each ease the experiments extend over 2 periods. At 
the close of the first period the plants were shifted in position 
and а second application of the spray mixture or dust was 
given. With the conclusion of the experiment the green weights 
of all plants were taken, thus enabling us to determine, in 
addition to the total transpiration quantities, the amount of 
transpiration per gram of green substance. 
2 
