1908] BRIEFER ARTICLES 225 
to approach the problem in a somewhat different way. If the absorptive 
power of the soil is a factor of real importance, so far as plant life is con- 
cerned, it would be reasonable to expect that a concentration of a given salt 
solution which has proved to be detrimental for a given kind of plant when 
grown in soil extract would be beneficial or at least do no harm to the same 
kind of plant when grown in the soil itself. 
With this idea in mind, we undertook (x) to determine the maximum 
tolerance of wheat seedlings to concentrations of certain salts when grown 
in soil extract to which known quantities of the salt in question were added; 
(2) to grow the same kind of plants in paraffined wire baskets,! using the 
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ae Ss “Y as FT pee 
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4 
5 
t.—Tolerance of wheat seedlings to solutions of NazgHPO,; roots . 
ej ey” re : oD: - 
ution: 1, distilled water; 2, soil extract (2:1); 3, extract +300PP™ POs; 
Fic, 
In the sol 
4; Sa 500Ppm. ; ca 
rn Soon, x. Same + 700°P™; 6, same+1oooPP™; 7, same + 2000PPm, 
same kind of soil, making it up to the proper moisture content, and watering 
the Plants with solutions of the same salts, of concentrations equal to and 
higher than the maximum tolerance determined for the extract by cultures. 
Na,HPO,, KCl, and NaNO, were selected for use, separately and in 
Various combinations. Some of the results obtained with the phosphate 
“alt are given here. The extract was prepared by mixing a known quantity 
of air-dry soil with twice its weight of distilled water, leaving the mixture, 
With occasional stirring, for 48 hours, and filtering off the liquid. Portions 
' The method devised by the Bureau of Soils, U. S$. Dept. Agric. (see Bull. 23 
and others of the Bureau) 
