CELL MEASUREMENT 197 
Phaseolus there is a physiological limitation to the length which can 
be attained by a cell without undergoing division. 
Plant physiologists recognize, of course, that there is presumably 
for each kind of cell a specific size at which division takes place. The 
evidence, in the case of primary meristem, is based upon such experi- 
ments as those of Newcombe* in which growing tips were incased in 
gypsum, in order to prevent growth by mechanical means. Under 
such conditions the primary meristem ceases division, and does not 
resume it until the release of the pressure permits the growth of the 
cells to the specific size at which division takes place. The somewhat 
differentiated epidermal cells present a different condition. The 
cells are in a state of extension, accompanied by increase in volume of 
the vacuole, but not, as far as known, by any increase in the amount 
of protoplasm. Although it is quite in accord with expectation to find 
that cells in course of extension, providing they retain the meriste- 
matic function, should have a specific size for division, it is nevertheless 
a distinct gain to have additional data bearing upon the subject. 
Table I 
Length in Mm. of Primary Epidermal Cells {including both Divided and Undivided 
Cells) of Epicotyl of Phaseolus multiflorus Grown in Light. {The Sections 
are Numbered from the Basal Tenth {No. i) upwards) 
Class 
Section 
Entire 
Internode 
I 
2 
3 
4 
5 
6 
7 
8 
9 
10 
.030-057 
9 
12 
7 
I 
0 
I 
I 
0 
0 
2 
33 
.060-087 
47 
45 
37 
13 
2 
II 
3 
6 
5 
9 
178 
.O9O-.II7 
37 
25 
33 
24 
18 
15 
13 
29 
15 
21 
230 
.I2O-.I47 
7 
17 
22 
26 
23 
26 
24 
20 
33 
26 
224 
.I5O-.I77 
I 
I 
21 
22 
20 
27 
17 
23 
23 
155 
.180-.207 
12 
12 
15 
18 
10 
15 
15 
97 
.2IO-.237 
2 
12 
6 
8 
II 
4 
3 
46 
.240-. 267 
I 
5 
5 
4 
I 
3 
I 
20 
.270-.297 
2 
I 
2 
2 
I 
8 
.300-327 
3 
3 
0 
6 
.33O-.357 
0 
I 
2 
.360-.387 
I 
I 
Tables I and VI give the frequency distributions for the primary 
cells, disregarding secondary divisions. That is to say, the measure- 
ments were taken from end to end of the sharp-pointed outline of the 
^ Newcombe, F. C. The influence of mechanical resistance on the development 
and life-period of cells. Bot. Gaz. 19: 149-157, 191-199, 229-236. 1894, 
