SALINE AND ALKALI LANDS. 



529 



transmission of heat. When salt-tolerant plants are grown on 

 saline soils, their palisade cells are relatively lengthened. 



Coincident with these external means for the retardation 

 of evaporation, the leaves of xerophiles are frequently sup- 

 plied with special water-storage cells, which supply moisture 

 for the physiological processes when the root supply falls 

 short. The cactus trihe and similar-looking plants are ex- 

 amples of the latter provision, which causes even animals 

 suffering from thirst to resort to them, although they eschew 

 the saline vegetation. 



Absorption of the Salts. The true halophytes or exclusive 

 salt plants, which refuse to grow on lands not containing a 

 large proportions of salt, often absorb so much salt that on 

 drying it blooms out on their surface; they usually have, even 

 when green, a distinctly salty taste, and their ash is rich in 

 chlorids, specially of sodium. Such is the case of the 

 samphire, common in saline marshes everywhere. The total 

 ash is usually very high, often varying with the salinity of 

 the water or soil in which they have grown. Thus the salt- 

 content of the ash of samphire may vary by several per cent. 

 In other cases, as in that of one of the Australian saltbushes 

 investigated at the California station, neither the ash content 

 nor the composition of the ash varies materially whether the 

 plant be grown on strong alkali land, or on uplands whose 

 total saline content does not exceed (in four feet depth) 

 .015' r or 2500 pounds per acre. 



The following table gives the composition of the ash of 

 this saltbush alongside of that of two other prominent alkali- 

 plants of the same relationship, occurring, one in the San 

 Joaquin valley of California, in strongly saline lands, the 

 other in the (treat 1'asin region of the interior, on lands 

 strongly impregnated with carlxmate of soda. All these, it 

 will be seen, take up very large amounts of sodium salts. 

 notably the chlorid ; the Australian plant most so. the " grease- 

 wood " of the Great I>asin least so; a large proportion of the 

 alkali salts being evidently, in the latter case, contained in the 

 form of organic salts, which in the ash become carbonates. 



It will be noted that the saltbush hay contains nearly one- 

 fifth of its (airdry) weight of ash. of which nearly 4O r r is 

 common salt. It therefore has a distinctly salty taste, and is 

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