THE QUESTION OF THE TOXICITY OF DISTILLED WATER 397 
the decay of organic matter. It must be admitted that these investi- 
gators have collected a vast amount of facts to substantiate this 
theory. In Bulletin 23^^ it is shown that the bad characteristics of a 
soil are transmitted to its aqueous extract. The injury to wheat 
seedlings grown in this as compared with their growth in an aqueous 
extract of a good soil, could not be attributed to a difference in nutritive 
salts for they analyzed practically the same. The conclusion was 
drawn that the solution contained injurious substances which checked 
the growth of plants. In Bulletin 28^^ it was shown that wheat seed- 
lings give off substances which are toxic to themselves. This is true 
when seedlings are grown in nutrient solutions which have been 
previously used for growing plants. Carbon black or ferric hydrate 
corrects the used solution so that it produces nearly as good growth 
as the fresh one. The same is true when distilled water is used 
instead of the nutrient solution. "These results with distilled water," 
the author states, "seem to make it very certain that the roots of 
seedling wheat plants do give off substances which are poisonous to 
themselves, and these substances can be corrected by carbon black 
or ferric hydrate." This recalls to mind the experiments by Macaire^^ 
in 1832, who noted that peas grew poorly in water containing excre- 
tions from the roots of the same plants, while wheat on the other hand 
did well in water charged with the excretions from pea roots. Later, 
1845, Boussingault^^ studied the question of root excretion and came 
to the conclusion that plants do not normally excrete materials from 
their roots, but may do so in water culture. 
For a more extended account of the earlier literature and especially 
that of the work of the Duke of Bedford and S. U. Pickering on the 
deleterious effect of grass on fruit trees, the writer wishes to refer the 
reader to Bulletin 36 by B. E. Livingston, and the works of Schreiner 
and his assistants, found in bulletins of the Bureau of Soils, U. S. 
Department of Agriculture, Nos. 47, 53, 70, 74, 75, and 80. 
What we are most concerned with at the present time is the possi- 
Whitney, M., and Cameron, F. K. Investigations in Soil Fertility. U. S. 
Dept. Agr. Bur. Soils Bull. 23. 1904. 
1^ Livingston, B. E., Britton, J. C, and Reid, F. R. Studies on the Properties 
of an Unproductive Soil. U. S. Dept. Agr. Bur. Soils Bull. 28. 1905. 
13 Macaire-Prinsep, Memoire pour servir a I'histoire des assolemens; Mem. Soc, 
Phys. Hist. Nat. Geneve, 5: 282-302. 1832. 
20 Boussingault, J. B. J. D. Rural Economy. Trans, by George Law (London), 
345. 1845- 
