ARTICLES 69 



The only way of solving the difficulty is to grow the plants 

 in culture media to which chlorides have been added, and to 

 make periodical chemical analyses both of the culture medium 

 and of the plants. 



TRANSPIRATION 



The facts relating to the absorption of water by means of 

 the roots lead naturally to a consideration of the transpiration 

 of water, for, if this be low, the conditions inseparable from a 

 saline habitat, which is generally considered to mean physio- 

 logical drought, need not be so spartan as is often supposed. 

 On purely anatomical grounds, 1 the facts that in Salicomia 

 and Suceda the cuticle is very thin, and the stomates are 

 superficially placed ; that in two such typical halophytes as 

 Salicomia and Aster Tripolium the stomates are essentially 

 mesophytic in character — since they are superficially placed, 

 are capable of movement and are sensitive to changes in the 

 intensity of light and in the humidity of the atmosphere — 

 indicate that transpiration is not abnormally low. But 

 against these must be set the facts that the cell-sap is acid ; 

 that the stomates are less numerous per unit area as compared 

 with a typical mesophyte such as Vicia cracca ; that the stomata 

 in some cases, e.g. Suceda maritima, are apparently always 

 closed, or, in other instances, lose their power of movement 

 and remain closed at the flowering period, e.g. Salicomia; and 

 that water-storage tissues may be present. 



It has been found by experiment that the transpiration of 

 the plants in question is remarkably high. But, before passing 

 on to a consideration of these investigations, brief mention 

 may be made of the relationship between stomates and tran- 

 spiration in the present connection. 



It is a difficult question to decide to what extent the 

 stomates of succulent plants are capable of regulating tran- 

 spiration. Delf 2 considers that the limiting power of stomates 

 may be greater than is generally supposed, for when the 

 guard cells are apparently closed a regulation of size in the 

 outer respiratory chamber may be demonstrated. 



The cut ends of two healthy and similar shoots of Salicomia 



1 Delf, Ann. Bot. 25, 485, 191 1 ; de Fraine, E., Journ. Linn. Soc. Lond. Bot. 

 41, 317, 1913. 



2 Delf, Ann. Bot. 26, 409, 191 2. 



