19141 
DUGGAR AND COOLEY—FILMS AND TRANSPIRATION 7 
with the observation of Rumm and others regarding the higher 
assimilatory activity in sprayed plants. 
It is unnecessary in this report to review the considerable 
literature which has accumulated bearing on the question of 
increased starch formation as a result of the application of 
Bordeaux mixture, especially as it is proposed to discuss this 
phase of the subject in a later paper. 
METHODS 
As indicated in the title, the experimental work here reported 
is concerned merely with the transpiration of sprayed and un- 
sprayed leaves or plants. Other effects of sprays and dusts 
may be communieated in subsequent reports. In general, 
the methods involved are modifications of customary practices. 
The methods used were of two types, the experiments being 
carried out either by means of (1) leaves in burette potometers 
connected with side arm flasks, or (2) potted tomato plants. 
Potometer Experiments.—After much preliminary experimen- 
tation with a view to determining suitable leaves or twigs 
for potometer work, leaves of the castor bean were selected. 
Some of the preliminary experiments with other leaves are of 
interest, however, and will be referred to subsequently. Castor 
bean (Ricinus communis) leaves offer some special advantages, 
especially (1) large surfaces, (2) resistance towards Bordeaux 
mixture, and (3) prolonged vitality after abscision. 
The burettes were connected with the side arm flasks, as 
indicated in plate 1, and the flasks completely filled with water. 
The petioles of the leaves were cemented into the mouths of 
the flasks by means of “‘plastolina.” If a ring of this plastic 
substance is placed around the mouth of the flask when the glass 
is dry and a ball of the same material, larger than the mouth 
of the flask, is carefully attached around the petiole, then the 
petiole and plastolina may be plunged into the mouth of the 
flask and the two masses unite in a manner such as to give a 
perfectly air-proof, water-tight connection. It has been found 
desirable, for purposes of safety, to put on a second layer of 
the plastolina as soon as it is evident that the first permits no 
leakage. Even with these precautions, considerable diurnal 
changes in temperature may cause leakage, and it is particu- 
