1904] BENNETT: ARE ROOTS AEROTROPIC 249 
The duration of the experiments was necessarily short, since 
the roots could not be readjusted to the air chamber without 
altering the conditions. It is noticeable that of the 143 seed- 
lings thus tested, 16 turned toward the air chamber, 18 away, and 
109 were not responsive. The angles were generally very slight. 
In the foregoing series of experiments, in which the roots 
were immersed in water with the oxygen pressure so reduced as 
to retard growth beyond the usual retardation in water, the pres- 
Fic. 3.—A, chamber filled with various gases; 8, chamber containing air; C, 
chamber connecting 4 and &; a, glass side-wall of chamber C,; 6, cork sealed in end 
of chamber C; «¢, opening into bottle; @, position of groove; ¢, seedlings; f, cotton 
around seedlings. 
ence of air within a few millimeters of the root tips induced no 
aerotropic curves. 
2. With roots in damp chambers. 
Because of the slow diffusion of gases in water, other results 
Were anticipated on growing seedlings in damp chambers. To 
this end an apparatus (fig. 3) was constructed consisting of two 
eight-liter bottles (A and B) which were connected near their 
bases by a rectangular chamber (C) whose inner dimensions were 
15™ by 3™ by 1. This chamber was covered entirely with 
plaster of Paris, except along the sides, where the plaster was 
removed to expose the inner side walls of glass (a). A large 
cork (4) was sealed into each end of the chamber, through which 
