Turgor and of Temper attire on Growth. 367 
were resumed. The causes here active receive further mention 
below. 
Regarding the results of investigations made with higher 
plants, we find it noted by de Vries 1 that the growth of 
roots of seedlings and of stems in a 3 per cent, solution of NaCl 
was greater during the first twenty-four hours than during the 
like period immediately following. He further observed that 
the effect of a sudden change of turgor in the cells of 
certain flower stalks was similar to that noted in the Siphoneae 
and in the moulds. Upon washing out the tissues under the 
microscope, after five hours in a 7 per cent. KN 0 3 solution, 
many of the protoplasts were seen to burst before coming 
into contact with the cell-wall. 
Stange 2 observed that sudden changes of medium were 
fatal to roots of Vida Faba , Pisum sativum , and Lupinus 
albiis when the extremes of concentration involved were 
sufficiently removed from one another. Root-hairs were 
burst as a result of turgor-change. 
From the observations cited, it appears that the condition 
of protoplasm and its rate of growth are more or less affected 
by a sudden change of the concentration of the substratum. 
In the cellular plants, as a result of the withdrawal of water 
from the cell-sap by an external solution of greater osmotic 
activity, the turgescence of the cells is diminished, and for 
mechanical reasons growth is either reduced or is stopped. 
On the other hand, a sudden increase of the water supply to 
a plant that has accommodated itself to a high concentration, 
causes the cells to take up water from the more dilute medium 
until an equilibrium is established. Thus the turgor pressure 
is increased, and an elongation due to this mechanical cause 
takes place, or tends to take place. It follows that the change 
of concentration must involve a certain minimum of difference, 
in order to call forth a noticeable change of length. The 
1 H. de Vries, Untersuchungen iiber die mechanischen Ursachen der Zell- 
streckung. Leipzig, 1877, P* 58. 
2 B. Stange, Beziehung zwischen Substratconcentration, Turgor und Wachsthum 
bei einigen phanerogamen Pflanzen. Bot. Zeit. 1892, p. 253. 
D d 2 
