332 BOTANICAL GAZETTE [MAY 
illuminating comparisons were obtained from this material. 
In order to determine, if possible, the nature of the changes 
induced in the motor zone previous to reaction, seedlings were 
placed in such position that the radicles pointed nearly vertically 
upward. After a time, approximately equal to the latent period 
of the organ, the motor zone was bent mechanically in the plane 
in which curvature would have ensued if the roots had been 
allowed to react normally. The bending and killing was accom- 
plished as above. 
Traumatropic curvatures were produced for the study of the 
motor and sensory zones as follows: The tips of roots were 
touched with acetic acid or a hot rod, or cut with a razor in the 
manner described by Spalding (28), and then the seedling 
was placed in a moist chamber or moist sawdust. Roots which 
were to be placed in the moist chamber could be branded by 
means of a glass rod heated in the yellow gas flame. The 
adhering portion of carbon served to mark the location and 
direction of the branding. It is to be said that in general trau- 
matropic reactions exhibit a much longer latent period than 
those of geotropism. In some instances branded roots were 
placed in such position as to be geotropically excited at the 
time, although no uniform acceleration of curvature was thus 
obtained. 
So far as the information of the writer is concerned, it does 
not appear that any attempt has been made to obtain the 
anatomical details and stature of the cells of the motor zone 1m 
a root in which the curvature recently produced has been 
straightened by an excitation in the opposite direction. No 
exact data are accessible, but almost all of the writers who have 
deait with the subject are unanimous in the agreement that 
young curvatures may be straightened and equalized. The 
material bearing upon this point was obtained by placing root 
tips pointing upward until various angles of geotropic curvature 
had been formed, and then by a half revolution of the 
portion of the root upon its axis and the proper lateral adjust- 
ment, the tip was brought into a position similar to the original 
