RESISTANCE TO BLACK ALKALI BY CERTAIN PLANTS. 



By Frank K. Cameron. 



IXTRODUCTION. 



While working in the San Joaquin Valle}', California, during this 

 l)ast summer one of the field jifii'ties of the Division of Soils observed 

 three species of plants which appeared to be characteristic growths on 

 soils containing much "black alkali" or sodium carbonate. Su^Der- 

 ficial examination in tlie field brought out the fact that the stems and 

 leaves of these three plants w^ere quite acid, in some cases very 

 markedlj^ so. A possible connection was suggested betw^een this fact 

 and the one first noted — that these plants were all found on soils con- 

 taining much sodium carbonate. Specimens were collected and sent 

 in to tlie laborator}^ for further examination. They were kindly 

 identified by Mr. Kearney, of the Division of Vegetable Physiology 

 and Pathology. They consisted of three samples of Disfichlis sjncata, y 

 numbered I, II, and III; one sample of Suaeda intermedia, w^hich w^as 

 separated into tw^o portions, the first numb'ered lY, consisting of the 

 stems alone, and the second numbered V, being composed of leaves 

 alo*ne; one sample of Afriplex hracteosa, wiiich was also separated into 

 a portion numbered YI, consisting of stems alone, and a portion num- 

 bered YII, consisting of leaves alone. 



Samples I, II, and III were thoroughly air dried b}' being allowed to 

 remain for about two months in the sacks in wiiich the}^ were received 

 at the laboratory. It should be stated that a rough determination of 

 the acidity they displayed was made as soon as the}^ were received in 

 the laborator}', and the results agreed fairly well with those obtained 

 by the more careful examination subsequently made. 



Samples lY, Y, YI, and YII were found to be very w^et and in seri- 

 ous danger of fermenting when received at the laboratoiy. Thej^ were 

 therefore placed in a hot-air oven and dried for several days at from 

 105° to 110°C. In each case the material was then cut into small 

 pieces and kept in carefully covered beakers, to which, however, the 

 air had free access. 



METHOD OF EXAMINATION. 



The method of examination w^as in all cases to steej) the sample, 

 which had been cut into small pieces about a centimeter in length, 

 overnight or for about twenty- hours in a convenient amount of dis- 



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