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of the apparatus to effect the cleaning. The bubbles produced by the Kekulé 
apparatus as well as that by Bunsen should be as small as possible. How- 
ever, it is not possible to constrict the submerged end of the tube much, 
otherwise the resistance to the passage of the bubbles and the water nee- 
essary to convey them will be so great as to prevent a sufficiently rapid flow. 
The Kekulé appartus while useful for airing a few cultures, is too small 
to furnish sufficient air for a series having a large number of cultures. I 
have therefore used for airing a series of seven or more cultures the Bun- 
sen apparatus above referred to. The pump portion of the Bunsen appa- 
‘atus was constructed by using the ordinary form of a large sized Chap- 
man’s brass air pump. For the tube below the Chapman pump I used 
an old condenser which had been broken and which had a diameter of 
about 5 em. This I cut off so that it had a length of 45 em. leaving 
near the end one of the lateral tubulares for the escape of air from the 
apparatus. This length of tube gave a column of water of sufficient height 
to easily force the air through the water culture solution in the 1.5 L 
capacity culture jars in which the depth was 20 em. From the Bunsen 
appartus arranged as just described I conducted the air through a lead tube 
having a bore of .56 em. and an external diameter of 1 cm. a distance of 
about 11 meters to the water cultures. These cultures, in many eases 14 
in number, were placed about the center of the greenhouse in order to obtain 
the best light; otherwise they wouid have been placed nearer the pump. 
In order to prevent any possibility of water being blown over from the 
pump into the cultures a bottle was arranged so that the air passed into 
it and then out at the top before entering the cultures. This acted as a 
catch basin or pocket for the water in case any should pass through the 
lead pipe. In the use of the apparatus thus far, however, I have not ob- 
served that any water has been carried over to the bottle. This is prob- 
ably because the lead pipe rises to a height of 2 meters or more before 
the air enters the cultures. If water should enter the culture solution 
after passing through the lead pipe it would, of course, be poisonous to 
the plants. If water should pass from the Bunsen pump so used to the 
water culture, it would be less poisonous to the plants than if it were dis- 
tilled water. because as distilled water it is in the form of hydroxide of 
lead and would contain more lead, whereas in the case of natural water 
it is then in the form of carbonate of lead, which is less soluble and 
would contain less lead. 
In the form of the apparatus as first used to distribute the air to the in- 
dividual jars containing the culture solution I used a piece of cypress 5 em, 
broad by 55 em. long which carried two rows of T-tubes haying seven T- 
tubes in each row. The cypress board was perforated with holes which al- 
lowed the central arm of each set of seven T-tubes to project through the 
board on each side. These T-tubes were connected with one another and to 
the glass tubes that conveyed the air down through the culture solutions 
by rubber tubing. There were in all about 45 rubber tube connections. 
These were troublesome to keep free from leaks owing to the cracking of 
the rubber tubing. The life of the rubber tubing in such situations as here 
