i3 8 
Ami C. Halket. 
3. No quantitative relations can be deduced between the 
amount of water absorbed and the time of immersion, the weight of 
the succulent part of the plant, the weight of water in the succulent 
part of the plant or the dry weight of the plant. 
Some quantitative results might possibly have been obtained if 
the surface area had been used for comparison, but no measurements 
of area were taken. 
4. This absorption is due to the high osmotic pressure of the 
cell-sap since non-halophytic plants lose water during immersion. 
Many gaps are left by these experiments, but they are, perhaps, 
worth recording as they show that certain typical salt-marsh plants, 
especially under conditions of drought, are capable of absorbing 
water through the epidermal cells of their aerial parts, not only 
from precipitated atmospheric moisture, but also from a salt solution 
approximating in strength to that of the sea. No experiments were 
made to see what absorption took place from sea-water itself. 
It is impossible to tell without further experiment what is the 
importance of the part played by this method of absorption in the 
life of these plants. Their root-system is small in proportion to 
their size and it is probable that the amount of water absorbed by 
the roots is proportionally small. The water obtained from 
“ atmospheric moisture ” through absorption by its aerial parts may 
compensate the plant for this smallness of root-absorption. It is 
not suggested that the quantity of water absorbed from the sea by 
its aerial parts is of great importance to the plant under ordinary 
conditions, for this amount is small. It is suggested, however, that 
the water absorbed in this way may be especially useful to the plant 
in times of drought. Under these conditions the amount absorbed is 
greater, and the neceessity for it is increased as the amount of atmo¬ 
spheric moisture available is reduced. It is probable also that under 
conditions of drought root-absorption is diminished. For if, as is 
generally accepted, root-absorption is due to “ osmosis,” the rate at 
which water passes into the root-hairs must in part depend on the 
difference of concentrations of their cell-sap and the surrounding 
liquid. Hill 1 has shown that the osmotic pressure of the root-hairs 
of Salicornia seedlings can adjust itself in response to a change in 
that of the surrounding medium. There is no reason, however, to 
suppose that the ratio between the osmotic pressures of the cell-sap 
and that of the surrounding liquid remains the same. 
Op. cit. 
