io8 BOTANICAL GAZETTE [February 



elusion that the chlorids produce abnormal conditions in the plants 

 and disorders in the nutritive processes. In this regard most writers 

 agree, but in explaining the means by which the plant neutralizt 

 this injurious effect of common salt there is a wide divergence of 

 opinion. While Schimper maintains that the structural adaptation 

 of halophile plants are caused by the necessity of keeping the rela- 

 tive amount of sodium chlorid in the cell-sap below the specific danger 

 point, Diels (6) considers that this is effected by chemical decompo- 

 sition of the salt. This process is not known, but Diels assumes that 

 in respiration the succulent halophytes differ from other plants in that 

 the oxidation does not proceed so far in halophytes, but stops at malic 

 acid or some isomer, with which the cell-sap becomes saturated, while 

 only small quantities of carbonic acid are evolved. The malic acid 

 then combines with the hydrochloric acid and is excreted by the root 

 Benecke (2) has severely criticized these conclusions of Diels. 

 In regions having a hot climate the evaporation of water is very 



great 



The 



concentration of salts is also increased in countries where the rain falls 

 only during a rainy period, leaving a long time in which no leaching 

 of the salts takes place in the soil. In places with frequent rains the 

 salts are rapidly washed out and carried deeper into the ground, until 

 the lateral flow of water toward the sea is encountered. 



The observations on salinity of strand sand made by the author 

 are all based on chemical analysis. The electrical method of deter- 

 mining the salinity as employed by the United States Bureau of Soil? 

 was not familiar to the author at that time, but careful observations 

 and determinations of the salinity with that method ought to reveal the 

 causes of distribution of certain plants on the strand. The writer 

 has found that the small embryonic dunes formed by certain strand 

 plants contain a greater amount of salts than tJwse occupied by others. 

 Thus, for instance, the small, embryonic, Elymus arenarius dune? 

 always contain 0.005-0.009 per cent, more sodium chlorid than the 

 Ammophila arenaria dunes. Likewise the Mesembryanthemum 

 dunes on the California coast have a higher salinity than the Abronia 

 dunes, while the elevations formed by Abronia latifolia contain m« re 

 salt than A. umbellata hummocks. These are the only examples 

 which have been verified hv nnalv™ k„f 



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