Osmotic Properties of Salt Marsh Plants. 141 
3. In any area the osmotic strength varies with the 
physiological scarcity of water. 
4. In all plants growing under the same conditions the 
osmotic strength of the cell is generally the same. 
In all cases the authors used either the epidermis or the 
mesophyll of the leaf. 
The results obtained from the study of Salicornia and Suaeda 
are in agreement with those of Dr. and Mrs. Drabble, with 
possibly two exceptions. Firstly, my observations tend to show 
that there is a variation in the osmotic strength of different 
individuals growing in the same locality ; and, secondly, the osmotic 
equivalent of salt-marsh plants may be very much higher, in fact, 
double that given (-51 gm. mol. of NaCl.) by our authors. These 
divergencies are probably of no importance ; for, in the first case, 
the seeming difference may be due to the fact that leaf-tissue was 
used in the one investigation and root-hairs in the other. In the 
second instance, the plants used were not the same; also, it has 
been shown how great may be the variation in the osmotic strength 
of one cell at different times, when subjected to different condi¬ 
tions; and, lastly, our authors do not give any observations on the 
salinity of the soil-water, which is an important factor bearing on 
the osmotic strength of the plant, and which might have been less 
at Burton Point, Cheshire, than that which obtains at the Bouche 
d’Erquy. 
To return to the salt-marsh plants; it is not proposed to dis¬ 
cuss, on the present occasion, the mechanism by means of which 
the internal osmotic pressure of the root-hairs is regulated: it may 
be due to chemical changes in the organic substances of the cell- 
sap, or, to the absorption of sodium chloride from the surrounding 
medium. As regards this last possibility, it may be remarked 
that no trace of sodium chloride was found in the root-hairs on a 
preliminary analysis; but this is a point which will have to be more 
fully investigated. 
The following is a summary of the chief facts observed, other 
than those dealt with above. 
1. The osmotic pressure in different root-hairs of the same 
individual plant varies; as a rule the younger hairs have a higher 
equivalent. The cells of the root cap have a very low co-efficient. 
2. The osmotic pressure in the root-hairs may vary in 
different individuals of the same species. 
