Wounded Plants. 
535 
bottle by means of a cock. Through the other hole in the 
stopper was passed a piece of ordinary tubing, which projected 
a short distance down into the bottle. To this end was 
attached a rubber-balloon with very stout walls capable of 
considerable expansion ; while the other end, bent at a short 
distance above the stopper, led off to a bottle filled with 
water, to which was attached an air-pump. When a few 
strokes were given to the air-pump, the water in the bottle 
referred to was forced into the balloon, thus expanding it 
to three or four times its original capacity, by which an appre- 
ciable pressure was produced in the receiver. Reference to the 
figure (woodcut 2 ) will explain the details of this apparatus. 
The whole receiver was immersed under water until the stopper 
was well covered, to ensure both perfect closing and a tolerably 
constant temperature. As the temperature of the laboratory 
was fairly regular, it was possible to keep the receiver within 
at most one degree of the same temperature with compara- 
tive ease. 
The mode of operating was as follows. The samples of 
plants under investigation were put into the receiver, and 
after a current of air had been passed through it the stopper 
was fixed tightly in place and the whole clamped in position 
under the water. The cock leading to the delivery-tube was 
closed, and the glass tube from the rubber-balloon connected 
with the air-pump. Two or three strokes of the air-pump were 
given, and the balloon so expanded was allowed to collapse 
to drive out the air which it contained. The apparatus was 
then allowed to stand until the time for the experiment had 
expired, upon which a sample of the contained air was taken 
as follows. The balloon was first filled and emptied three or 
four times to procure a thorough admixture of the gases in 
the receiver ; this was found by actual experiment with smoke 
to be thoroughly accomplished in three repeated fillings and 
emptyings. Finally the balloon was once more distended, 
the end of the capillary-tube thrust under the mercury, and 
the cock at once opened. A very considerable stream of gas 
was thus forced out, of which the first few cc. were rejected to 
