198 Aeration [396 



with chromium imply that it may form an exception to this 

 behavior, but even with this element it was observed that 

 Pelargonium leaves were injured only when of middle age; 

 young and old leaves being unaffected. 



THE EFFECT OF AERATION ON THE GROWTH OF 

 BUCKWHEAT IN WATER-CULTURES 



By E. E. FREE 



In connection with other work on the oxygen requirements 

 of plant roots experiments have been made on the relations 

 between the degree of aeration of the culture solution and 

 the growth of buckwheat in water-cultures. The plants were 

 grown in quart jars in the usual manner, three plants to a 

 jar. The solution was that found by Shive 1 to be the best 

 for the growth of buckwheat. The experiment included 18 

 jars divided into six sets of three jars each. One set, used 

 as control, was handled according to the usual technique, with 

 free access of air to the solution. Another set was sealed, 

 the seal about the young plants being made with a parafme- 

 vaseline mixture according to the method of Briggs and 

 Shantz. 2 With the third set, a slow stream of air was bubbled 

 through the culture solution, a bubble about 5 mm. in diam- 

 eter passing about once a second. The three remaining sets 

 were treated in the same way with oxygen, nitrogen and 

 carbon dioxide, respectively. Precautions were taken to re- 

 move deleterious impurities from the gases. Water evaporated 

 from the culture solutions was replaced when necessary. 



The cultures with oxygen, nitrogen and air showed no de- 

 parture from the open controls or from the sealed cultures. 



1 Shive, John W., " A three-salt nutrient solution for plants." 

 Amer. Jour. Bot. 2: 157-160, 1915. 



2 Briggs, L. J., and Shantz, H. L., "A wax seal method for deter- 

 mining the lower limit of available soil moisture." Bot. Gass. 51: 

 210-219. 1911. 



