462 BOTANICAL GAZETTE [December 



The flasks were stoppered with cotton plugs, each provided with a 

 glass tube passing through the center, this tube also being plugged 

 with cotton. The culture flasks with solutions were sterilized in 

 the autoclave for 30 minutes at 15 pounds pressure. 



When the seedlings were of adequate size, they were transferred 

 to the culture vessel. Transfer was made when the roots reached 

 the bottom of the tube and were curled about, and the tops had 

 attained a height of about 5 cm. By use of a heavy platinum 

 needle, the tube, together with tTie inner core of agar and the 

 seedling, was withdrawn from the test-tube and transferred to 

 tube 4 of the culture vessel (fig. 2). The tube 4 was slightly drawn 

 at the base so as to prevent tube 2 from passing through into the 

 culture solution. Sterilized cotton was then packed about the 

 seedling in tubes 2 and 4. The cultures when set up appeared as 

 shown in fig. 2. After being kept for a few days in the laboratory, 

 the cultures were transferred to the greenhouse. 



The particular advantage of this form of culture, from the 

 standpoint of studying the secretion of enzymes by the roots, is 

 that the seeds are kept entirely out of contact with the culture 

 solution, and any enzymes derived from the seeds are held in the 

 agar, which with the passing of time loses its water and hardens 

 to a flaky mass. 



In spite of all the precautions taken, cultures occasionally 

 became contaminated. All such cultures were rejected. At the 

 conclusion of the experiment, the culture solutions were brought 

 to the original volume and analyzed. In the first cultures, tests 

 were made for contaminating organisms, but these and other 

 similar experiments indicated that if the culture solutions were 

 clear at the conclusion of the experiment there was no contamina- 

 tion. Consequently, in the later experiments, no platings were 

 made of the culture solutions. Data were collected also on the 

 weights of roots and tops. Detailed methods of procedure are 

 described under the different experiments. 



For the first experiment two cultures were set up, following the 

 method described, using 2 1. flasks, in each of which was placed 

 1800 cc. of the culture solution containing 0.25 per cent of soluble 

 starch. A variety of corn known as Learning was employed. The 



