220 HALOPHYTES SECT, vn 



laria media, Salsola Soda whereas other species are unchanged ; and 

 conversely, that certain inland species when cultivated in a substratum 

 treated with common salt acquire thicker leaves, as is the case with Lotus 

 corniculatus and Plantago major. This thickness of leaf is caused by an 

 enlargement of the mesophyll-cells, which become large and roundish, 

 and, in the interior of the leaf, poor in chlorophyll, so that they are hyaline 

 and form an almost true aqueous tissue. In some cases a typical aqueous 

 tissue occurs and is surrounded by palisade tissue, for instance in Salsola 

 Kali, 1 Batis maritima, 2 Salicornia. 3 



Mucilage-cells are developed, as in xerophytes. Hypodermal aqueous 

 tissue is met with in species possessing more coriaceous leaves, for instance 

 in mangrove-plants (which may also possess large mucilage-cells, e. g. Son- 

 neratia), and in the grass Spinifex squarrosus. 



Cell-sap. Large quantities of salt may occur in the cell-sap and cause 

 the solution to be more concentrated than in the soil. 



The palisade tissue of halophytes is massive. Lesage 4 has experi- 

 mentally proved that the individual cells become taller, and often divided 

 transversely ; common salt acts morphologically approximately in the 

 same manner as sunlight. According to Schimper, 5 the leaves of plants 

 standing nearest to the sea in the Barringtonia-formation are thicker 

 than those of plants farther inland because their palisade tissue is larger. 



The intercellular spaces are small. 



The majority of species are leaf -succulents (Grisebach's ' chenopod- 

 form'); some are stem - succulents with reduced foliage-leaves, as in 

 the asclepiadaceous Caralmma. 



Succulent halophytes, as a rule, show a dark-green colour which later 

 on passes over into yellowish-green or red ; on certain steppes near the 

 Caspian Sea, when all else has been dried up by the sun, the solitary 

 green patches visible to the eye are on saline soil. Lesage proved that 

 side by side with an increase of common salt in the plant goes a decrease 

 in the amount of chlorophyll, and that this is due to the reduction in size 

 and number of the chloroplasts. In accordance with this seems to be 

 the fact established by Griffon 6 that the assimilatory activity is less in 

 the halophytic form than in the ordinary form of the same species. 



Wax. Coatings of wax, causing a glaucous and mat surface, charac- 

 terize many species, including Eryngium maritimum, Triticum junceum, 

 Elymus arenarius, Crambe maritima, Mertensia maritima, Glaucium 

 flavum, and Spinifex squarrosus. 



Hair-coating. The majority of halophytes are glabrous. Yet some 

 species possess hairs, though only rarely do they have soft or grey hairs, 

 as in Kochia hirsuta, Senecio candicans, and Tournefortia gnaphalodes. 

 Halophytes possessed of hairs are generally sand-plants ; some have 

 special water-storing hairs, 7 whose large, spherical, thin-walled, pearl-like, 

 terminal cells filled with sap fall off or collapse to form a grey coat ('meal '), 

 as in Atriplex, Obione, and Mesembryanthemum. 



Coriaceous and glossy leaves occur on trees and shrubs in mangrove- 

 swamps, and in allied vegetation, for instance in Rhizophora, Bruguiera, 

 and Nipa fruticans, also in sandy littoral forests. 



1 Areschoug, 1878. * Figured in Warming, 1890, 1897. 



3 Warming, 1906, Fig. 77-84. ' Lesage, 1890. 



5 Schimper, 1891. Griffon, 1898. 7 Seep. 121. 



