1916} ROBERTS—EPIDERMAL CELLS OF ROOTS oo ae 
of a cortical cell, and on side z it is exposed directly to the varying 
external conditions. 
In fig. 2, which is a median section of fig. 1, the following factors 
need to be considered: (1) air medium, (a) the physical character 
of walls z, 2, 4, 6; (b) the chemical nature of walls 1, 2, 4, 6; 
(c) the osmotic pressure on both 
sides of walls 2,4,6,and inside | 2 
I; (2) liquid medium, (a) the ‘ 
physical character of walls r, 
2, 4, 6; (b) the chemical nature : 
of walls z, 2, 4, 6; (c) the K wre neces 
osmotic pressure on both sides © 
of walls 1, 2, 4, 6; (3) length of . 
cells. 
Fics. 1, 2.—Fig. 1, form of an epider- 
A few measurements were mal cell; fig. 2, median section of fig. 1. 
made of the length of walls of 
cortical cells in comparison with the length of adjoining haired and 
unhaired epidermal cells. These were taken upon the same corn 
4 4 
Fic. x Fic. 2 
TABLE II 
pC, eran 35 30 
‘ inh caer eae 45 30 
gga sue aa a 37 — 
ee Aye Nar 60 50 
geen CRS eee 44 40 
adie OAS eye oa 37’ 55 
Oe eae es 40 50 
We ee aad aay 20 10 
ae ne ee 40 40 
s 
Ge ee eee Oe ee 8 8 e 
Viahees 2. ae: 40 80 
pe OR Gera 45-40 80 
Oo ene oes 40 4o 
Wo GS hese 20 20 
Be eS 12 20 
A NE EE 32 42 
root, the haired epidermal cells being those just above water and 
the unhaired just below water, with the results shown in table II. 
These measurements, although few, indicate that there is no 
