1897 ] THE CURVATURE OF ROOTS 339 
TABLE VI. 
Comparison of measurements of rows of cells in median longitudinal 
section of root of Zea excited geotropically for twenty hours and curved 
through 105 
MEASUREMENTS OF LENGTH. 
Ep. 2 | x re 5 6 | 7 Average 
een | 
Concave 19.6 | 18.9 29.3 28.8 19.2 25.2 31.9 24.7 
Convex 69.2 723 42.9 52.3 49.2 7.2 31.4 48.05 
| 
MEASUREMENTS OF WIDTH. 
| Ep. 1 | 2 | z | 4 | 5 6 | % Average 
| 
| | | | 
Concave Pol apes 8.25 6.62 7. ETE 15.7 | 21.4 11.4 
Convex eee 7.22 4.66 6.4 2 4 | 9.8 6.98 
An examination of the sections of which measurements are 
given in tables V and VI shows that the distance from the apex 
of the growing point to the cross section having the shortest 
radius of curvature is 2.24™™, and the width of the motor zone 
at its forward edge is 1.12™. The length of the cells from 
which the annular vessels will be formed is about two-thirds of 
that of these cells in a region at a distance of 1.5™™ in a basal 
direction from the region of greatest curvature. 
The granular density of the protoplasm of the epidermal 
cells of the concave side is less marked than in younger cur- 
vatures, and the external walls are thickened two to fcur times 
gia former diameter. Root hairs are abundant on the regions 
oth apical and basal to the region of greatest curvature, but 
are also wholly absent from che region exhibiting the shortest 
-Tadius of curvature, when the walls are most thickened. The 
Sub-epidermal cells are rectangular in outline, with the end walls 
‘Slightly oblique and exhibiting undulating foldings. The rows of © 
c cells in the fourth to the eighth layers have taken a contour 
: Bpicstive o of axial ioe cesar The axial walls gee in aradial 
