508 BROOKLYN BOTANIC GARDEN MEMOIRS 
these most dilute solutions is higher than is the case of those originally 
having a greater salt content, seeming to indicate that at this extreme 
dilution the plants are not only forced to yield ions to the solutions 
but are unable by reabsorbing them to reduce the concentration to a 
point lying much below the equivalent of 50 grm. norm. in a million 
liters. 
As the original concentration of CaSO, is increased to 31.3 and 
52.1 grm. norm. respectively absorption increases to a point showing 
net gains by the plants. Leaching of ions by the plants, if it takes 
place, is more than met here by their greater absorptive activity. 
This activity when greatest reduces the residual ion content markedly 
below that seen in the case of the originally more dilute solutions. 
It seems that with the addition of even slightly larger quantities of 
CaSOu, the absorptive function becomes more active and is able more 
nearly to exhaust the quantity of ions offered. 
As the quantity of CaSO, is increased to concentrations rising 
from 101.9 to 824.4 grm. norm. in a million liters the plants reduce 
the ion content of all solutions but absorption even at its greatest 
leaves a residue which increases as the quantity offered increases. 
Absorption, while in general increasing as the quantity of ions present 
increases, lags far behind the quantities offered. It thus comes about 
that the curve representing the residual ion content approximately 
parallels that representing the original ion content of the solutions. 
From these data it would seem that when squash seedlings are 
grown in darkness at 18° C. in solutions of CaSO, alone, they are 
unable to absorb as many ions as they lose when the solution contains 
less than about 30 grm. norm. of the salt in a million liters. When the 
solutions contain somewhat more than this quantity of this mixture of 
ions the plants can reduce the more dilute members of the series to an 
ion content of about the concentration seen at this equilibrium point. 
When the supply of ions is far in excess of absolute requirements, the 
seedlings absorb greater quantities than in weaker solutions but the 
quantity of residual ions left in the solution increases in nearly the 
same proportion as the quantity offered. 
In the following table (Table 2) are shown (1) the original con- 
centration of each solution, indicating the quantity of ions offered 
in each case; (2) the concentration of each solution at the time of 
maximum absorption, or the residual ion content of each solution and 
(3) the quantity of ions absorbed from each solution at the time of 
maximum absorption. 
