346 BOTANICAL GAZETTE [May 
MEASUREMENTS OF WIDTH OF CELLS OF CONCAVE SIDE. 
ical Basal Average 
0) a a a. a ae 
3 So ee oe GeO OG 9.375 
(3) 9 8 6 8 6 G -5F . fa 8 
De oe ee: a ce a 
(5) : 8 8 8 a) oo rne 8.71 
(6) 8 «8 a ee oe | 
pues width of cells, - : - . 8.4 
The root treated in the above manner offers a sequel to Noll’s 
bending experiments, by which the ductility of the walls of: the 
concave side of the stems was found to be diminished, or less 
than the normal. The region of curvature artificially produced 
coincided with that of geotropically excited roots, but it extended 
over the entire growing region of the tip in such manner that 
the extreme apical portion was bent only by the strains exerted 
upon it by the curvature artificially produced in the growing 
region. This fact disposes of the theory of Sachs that the entire 
apical portion is active in curvature. The region of shortest 
curvature in all of these experiments was found to be about 2™™ 
from the tip of the apical region, and the curvature decreased 
quite gradually apically and basally, as is asserted of the root in 
geotropic curvatures by Sachs. The form of such curvatures is 
undoubtedly due to the distribution of ductility in the different 
portions of the organ and the resultant curve approaches a 
hyperbola. In geotropic curvature the greatest bending occurs 
within very narrow limits in such manner as to favor the assump- 
tion that an increase in the ductility of the membranes has taken 
place here. 
_ The cortical region of the convex side has a width of .24™™ 
and of the concave side .25™™, the central cylinder .4™. 
The measurements given above show that actual eee 
of the superficial content of the cells of the convex side, and 4 
| diminution of those of the concave side has taken place, yet 
there i is no ‘apparent difference in the density of protoplasmic 
contents. The cells of the concave side exhibit plainly marked 
evidence of the oma which has been exerted upon them. 
