262 
R. H. TRUE AND H. H. BARTLETT 
centra tion, the loss being in general greater in the weaker solutions 
than in those more concentrated. The increased CO2 content of the 
solutions probably accounts in large part for the apparent loss of salts 
from the roots. The period of apparent loss to the solution was 
followed in the less concentrated cul- 
tures (20 to 60M X io~^) by a day 
during which no clear change took 
place. In the medium and stronger 
concentrations (80 to 260M X io~^) 
absorption proceeded at a gradually 
increasing rate. Beginning at about 
the fifth day in a majority of the cul- 
tures absorption proceeded at a rela- 
tively uniform rate until about the 
twelfth or fourteenth day, when the 
conductivities indicated either a slack- 
ening of absorption or a predominant 
loss of ions from the roots to the so- 
lution. The loss of electrolytes was 
probably due to the changes in the 
cells of the roots caused by approach- 
ing exhaustion from a lack of avail- 
able food. The root system showed 
little evidence of deterioration but a 
withering of the etiolated foliage leaves 
and even of the edges of the cotyle- 
dons took place. The hypocotyl some- 
times also broke down. 
The record of the weaker solutions 
(20 to %oM X io~*^) offers an interest- 
ing point. In the most dilute solu- 
tion {20M X io~^) the roots seemed 
to be unable to absorb activel}'^ at any 
time leaving the solution little chang- 
ed in its net ion concentration. In the 
solutions which had concentrations of 40 and SoMXiQ-^ respectively 
the roots were able to absorb actively after a period of delay decreasing 
in length with the increasing concentration of the solutions. After 
two weeks of absorption both reached a concentration similar to that 
1 
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> A 
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3 /* 
Fig. I. Curves showing the chang- 
es in concentration of the Ca(N03)2 
solutions used in experiment i. 
