572 Transactions. 



Scliimper (x) attributes it to tlie superaltundauce of salt in the soil ; 

 Warming (v) to an attempt to reduce the transpiring surface. Dr. Cock- 

 ayne, in his general account of the coastal vegetation of the South Island 

 of New Zealand, points out that the wind must be an important factor.* 

 This seems to be confirmed by the fact that those plants of the salt meadows 

 which have strayed into the marshes, or occupy the channels and are 

 sheltered by the dense growth of rushes or by the Plagianthus bushes, have 

 discarded to some extent the prostrate habit {e.g.. Atriplex, Selliera). The 

 direction of the prevailing wind is shown by the bushes of Plagianthus, 

 which in the more exposed situations are bent towards the west. It is a 

 well-known fact, however, that excess of light is not conducive to gro\rth ; 

 and here on the salt meadows there is a very bright illumination. May not 

 this account, in some degree, for the stunted growth ? 



(2.) A reduction of the leaves, both as regards number and size {Plagi- 

 anthus). In Salicornia they are entirely absent, while in Lepocarpus and 

 Juncus they are reduced to scales. This must be accounted for. as it 

 generally is, as a modification to reduce the transpiring surface. In the 

 case of Plagianthus, however, the wind, again, may be a determining factor 

 in the leaf-reduction, as well as in the adoption of a twiggy divaricating 

 habit. 



(3.) A more or less brilliant colouration, especially in the autumn, and 

 this in plants which are not deciduous {Selliera, Cotula dioica). The colour 

 here evidently is due, as Ganong (xi, p. 355) suggests, to the amount of 

 salt in the soil. Again, some exhibit a reddish colour, due to the presence 

 of anthocyan in the cells {Atriplex, Spergularia, (&c.). Many theories have 

 been advanced as to the use of this , pigment, one being that it acts as a 

 screen to the chloroplasts, to preserve them from injury from too intense 

 light (VII, p. 282). This would seem a very satisfactory explanation as far 

 as these halophytes are concerned, for on the level unshaded salt meadows 

 they are subjected to strong insolation. 



(4.) A great thickness of the leaves. This, perhaps, is the most note- 

 worthy of these characteristics, and will be dealt with more fully under 

 anatomical characters. 



(5.) Translucence of the leaves {e.g., Selliera, Spergularia). 



Some authors {i.e., Henslow, and Battandier, whom he quotes) give 

 hairiness as a very general character of halophytic plants ; but none of these 

 New Zealand halophytes show any hairiness, except Atriplex, with its 

 mealy tomentum of dead hairs, and Spergularia, with its sparse covering 

 of white hairs, almost invisible to the naked eye. 



Anatomical Characters of the Leaf. 



Epidermis : In some cases this shows a very much thickened cuticle 

 {Leptocarpus) ; but, on the whole, it is not strongly developed. The cuticle 

 often has an uneven surface, which in one case {Spergularia) became smooth 

 when plants were grown in pots. In all probability this uneven cuticle is a 

 definite adaptation, to guard, the leaf against the effect of the strong insola- 

 tion. In connection with the epidermis, again, glandular hairs are de- 

 veloped {Plagianthus, both species of Cotula, Samolus, Spergularia). These 



* This, of course, chiefly works by its ]ihysiological effect in transpiration, leading 

 to death through drj^ing-up of tissues. There is also a mechanical effect. 



