16 
namely, they had to be made on the tips of the main roots, which are 
not the places where the process is most active. In working with these 
solutions, trouble with red ants, which only exceptionally interfered with 
experiments with pure water, became serious; as a consequence I was 
finally obliged to seal all the tops of the bottle deeply with vaseline, thus 
completely cutting off the access of air to the water in the bottle; controls 
with pure water showed that during the time of these experiments very 
little if any interference with the absorption resulted. ‘The investiga- 
tions were made with the same roots which furnished the material for 
the preceding tables, and they immediately followed the conclusion of 
the period already reported. These results were scattered through too 
many days to make a tabulated report feasible. In each case the absorp- 
tion of the solution is compared with that of water during the preceding 
period, which usually was of one day. 
A solution of 0.1 normal reduced the rate of absorption for root VIT from 40 
centigrams (for the preceding twenty days) to 35 centigrams, which is within 
the limits of daily fluctuation. It was likewise questionable, in the case of main 
roots, whether there was any reduction by a 0.2 normal solution ; for instance, 
with root TI the rate actually increased from 14 centigrams to 15 centigrams. 
However, in the case of the three lateral roots, the rate fell from 51 centigrams 
to 16 centigrams, and after two days they were evidently unsound. 
The results obtained with 0.5 normal solutions were various. With root III 
the decrease in absorption was only from 18 centigrams to 8 centigrams; tested 
again with water, the rate rose to only 10 centigrams; another application of 
the solution reduced it to 7 centigrams; and in water it again rose to 10 cen- 
tigrams. With root I, the previous rate having been 7 centigrams, successive 
determinations were 1 centigram, 1 centigram, and 2 centigrams; in water the 
rate returned to 8 centigrams. With other roots the half-normal solution was 
found to be sufficient to reverse the movement. Thus root VI, which had been 
very regularly absorbing about 1 centigram, lost 2 centigrams, 3 centigrams, 
and 2 centigrams. Root VII lost 1 centigram at one time and the three fine roots 
lost at the same rate. 
Immediately after losing at the rate of 1 centigram for four days, root 
VIT was put into a normal solution, and it then gained 8 centigrams 
in one day. This result, which at first sight was surprising, is easily 
explained. Water moves through the root in the direction in which it is 
driven by the greatest pressure. Under ordinary circumstances this direc- 
tion is inward because of the influence of the atmospheric pressure, the - 
pressure within being less than that without. This may be expressed by 
stating that there is a “suction” from the inside. In using the more dilute 
solutions other agents must have acted together with the atmospheric 
pressure—agents which perhaps were put in operation by the solutions 
themselves; in this way the fact that the solution is absorbed will account 
for the result. With the half-normal solution the osmotic pressure was 
superior to the sum of the forces tending to make the water enter; as a 
result, it moved outward. Other roots may have absorbed this 0.5 normal 
