122 
Ann C. Halket. 
those found by Dr. and Mrs. Drabble, 1 for the salt-marsh plants 
Aster, Plantago and Festuca, from Burton Point, Cheshire. 
This high osmotic pressure is doubtless due to the fact that 
the sodium chloride absorbed by the roots accumulates in the cells 
of the succulent tissue. The analyses carried out by the members 
of the “ chemical section,” on the occasions referred to, show that 
the amount of sodium chloride present in the tissues was approxi¬ 
mately sufficient to account for the high osmotic pressures found. 
The variation5found in the osmotic pressures of the different 
plants is then not surprising, if it is largely due to the purely 
passive accumulation of salt in the tissues, for one would expect 
the amount to vary with the age and vigour of the plant. 
This assumption is rendered more probable by the fact that the 
few estimations made of the osmotic pressure of the cell-sap in 
cotyledons of Salicornia and Suceda gave lower results, -83 gm. mol. 
solution for Salicornia, and ’75 gm.-mol. solution for Suceda, 
than any made on mature plants. 
The point clearly brought out by the osmotic pressure deter¬ 
minations, that I wish to lay stress on here, was that the osmotic 
pressure of the cell-sap of Salicornia was always considerably higher 
than that of sea-water. The same thing is also true of the osmotic 
pressure of the leaves of Suceda maritima and Obione (A triplex) 
portulacoides. 
The Bouche d’ Erquy is covered by the sea about twelve times 
every fortnight during the spring tides ; the number of hours the 
plants are covered each time varying with the height of the tide, 
but being, of course, greatest in the lower lying parts of the marsh 
and those nearer the sea, where the Salicorniae grow most 
luxuriantly. The occurrence of the high osmotic pressure led one 
to ask whether it could not enable the plants to obtain water by 
absorption,- through the cells of the epidermis of its aerial parts, 
from the tides and from atmospheric moisture. It has long 
been known that many plants can absorb water through their 
leaves. This is well shown by the fact that flaccid leaves immersed 
in water, with the cut surface projecting, regain their turgidity. If 
then plants having an osmotic pressure of cell-sap corresponding 
1 Drabble and Drabble. “ The relation between the osmotic 
strength of cell-sap in plants and their physical environ¬ 
ment.” Bio. Chem. Journal, Vol. II, p. 117, 1907. 
2 After commencing these experiments, I saw the suggestion made 
by Drabble and Drabble in the paper referred to, that high 
osmotic pressures may enable plants to absorb water from 
the atmosphere. 
