16(1 



of the apparatus to effect the cleaning. The bubbles produced by the Kekule 

 aiilDaratus as well as that by Bunson should be as small as possible. How- 

 ever, it is not ])ossible to constrict the submerged end of the tube much, 

 otherwise the resistance to the passage of the bubbles and the water nec- 

 essary to convey them will be so great as to prevent a sufficiently rapid flow. 

 The Kekule 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- 

 ratus 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 w^hich had a diameter of 

 about 5 cm. This I cut off so that it had a length of 45 cm. 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 cm. From the Bunsen 

 appartus arranged as just described I conducted the air through a lead tube 

 having a bore of .5 cm. and an external diameter of 1 cm. a distance of 

 about 11 meters to the water cultures. These cultures, in many cases 14 

 in number, were placed about the center of the greenhouse in order to obtain 

 the best light ; otherwij^e they would 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 cm. 

 broad by 55 cm. long which carried two rows of T-tubes having seven T- 

 tubes in each row. The cypress board was iierforated 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 



