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. HE. 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* 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 parafine- 
vaseline mixture according to the method of Briggs and 
Shantz.” 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. 
*Shive, John W., “A three-salt nutrient solution for plants.” 
Amer. Jour. Bot. 2: 157-160, 1915. 
* Briggs, L. J., and Shantz, H. L., “A wax seal method for deter- 
mining the lower limit of available soil moisture.’ Bot. Gaz. 51: 
210-219. 1911. 
