Ee es Se Sige PY ee ae RE ee Sel eae eee IR NS bee eS 
1894.] The Influence of Mechanical Resistance. 235 
this article, the statement just made is founded principally on 
the behavior of the cells of the fundamental parenchyma. It 
was found in all cases where cells normally dying early were 
kept from reaching their full size that their life-period was 
extended. In certain cases also it was found that the pith of 
plants will live longer than usual if a gypsum cast is put 
around the stem after the pith has reached its full size, the 
cast, however, preventing the surrounding tissues of the stem 
from enlarging. It is probable that in the latter case, the 
pith lives because of the regulatory action of the plant, the 
buds a vegetative bud which developed into a shoot, and the 
flower axis instead of withering as usual lived to function as a 
vegetative axis. 
It is probable also that in the first group of experiments in 
Which the cells were not allowed to reach their normal size 
that the same Cause operated to prolong the life-period. Yet 
this Was 
of Funcus the cells remained alive though no greater demand 
— darkness, we have the direct evidence that it is not 
the use of the central cells for purposes of transport that keeps 
them alive. In such cases it is probable the cells in question 
i vain alive longer than normally because the conditions for 
theit existence are not so unfavorable; that is, they live be- 
oe the Surrounding tissues are not allowed by their growth 
coppulll these cells apart and thus bring them into unfavorable 
This question will be farther considered in a 
e. 
€xte ie eriments recorded in this paper have been peed 
life. néed enough in time to demonstrate the extension a. : 
the Period of the elements of the fibrovascular bundle. - 
in * clements also live longer than normally when surround- 
Stssues are not allowed to grow may be certainly inferred 
ns fos ebe. Jahrb. f. 
Is, Bot, ‘si ag abnormale Entstehung secundarer Gew J 
