[Vor. 1 
352 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
The apparatus is shown in pl. 18. The rack, or support, 
is made of a single sheet of galvanized iron 18 ст. wide and 55 
em. long, these dimensions being adequate for a stand 33 cm. 
high. Besides cutting a hole in the upper part for the insertion 
of the neck of the bottle, the operation of making a stand will 
be clear from the plate and involves merely a few slits with the 
shears, the balance being accomplished by bending. Two or 
four rivets may be used if additional strength is required. With 
regard to other features of the apparatus it is well to note that 
(1) the shoulder of the flower pot rests on the rim of a tin сар 
somewhat deeper than the pot, the latter containing the im- 
mediate supply of water; (2) there is an inverted bottle with a 
capacity of about 1500 сс. serving as a reservoir of water and 
aspirator; and (3) the bottle is connected with the cup by glass 
and rubber tubing. 
In setting up an experiment the exposed area of the pot 
(above the shoulder) and the soil are covered with paraffin or 
parawax; the cup is filled with water to such height that when 
the pot is inserted the water will rise to the height of about 
2 cm. on the side of the pot, thus insuring adequate absorption; 
while a notch in the side of the cup makes it possible to introduce 
the rubber tube connecting with the bottle, this tube being 
adjusted to reach just below the new level of water in the cup. 
With a tube of proper diameter, the water level in the cup is 
kept practically constant so long as the bottle contains water. 
This apparatus, complete, may be quickly and sufficiently 
accurately weighed on the Troemner scales. То prevent up- 
setting, after arranging in the experimental area, it is well to 
make the stand secure by providing a small hole in the base, 
through which a bamboo stick may be thrust into the soil. То 
this stake, also, for further support, the bottle may be fastened 
by соға or rubber band. 
Тһе deviee above described has saved much time and has 
enabled us to obtain a soil moisture content practically uniform 
in all the pots used in the experiment. It possesses the disad- 
vantage of tending to maintain а moisture content which “ог 
long-term cultures is too high for the best growth of the potato. 
A slight modification of the method would seem to be practi- 
cable in several aspects of transpiration work. 
