Society of Biological Chemists vii 
boron, added to manure for this purpose, on plant growth a study 
was made extending over 3 years in which crops were grown in 
different parts of the country on soil fertilized with manure 
containing definite amounts of added borax and of added coleman- 
ite. In order to test the cumulative effect of the boron the same 
plants were treated with manure and boron for three seasons. 
Wheat, rye, oats, beets, tomatoes, cowpeas, lettuce, soy beans, 
string beans, potatoes, spinach, kale, cabbage, turnips, corn, and 
peach trees were included in the experiments. 
Practically the same amount of boron was absorbed by the 
plants whether it was added to the soil as soluble borax or as 
insoluble colemanite. Wheat, oats, and rye absorbed little 
boron, while leguminous and succulent plants absorbed com- 
paratively large amounts. There was a marked difference in 
the distribution of the boron in the roots, tops, and fruit of the 
different plants. Leguminous plants were very sensitive to the 
boron. At Bethesda, Maryland, 0.0044 per cent H;BO; added 
as borax and 0.0058 per cent added as colemanite to the upper 6 
inches of soil caused no injury to lettuce, spinach, and kale, while 
at Arlington, Virginia (5 miles distant), the same amounts of 
boron gave a reduced yield of these crops. A similar difference 
in the effect of a definite amount of boron on other plants when 
grown on different soils is indicated. There is a decided differ- 
ence in soils in rendering the added boron non-toxic, although all 
soils tested gradually rendered the soluble boron insoluble and 
non-toxic. In many soils there is a tendency for plants to ab- 
sorb boron in proportion to the amounts added to the soil while 
in other soils the same amounts of boron were absorbed irrespec- 
tive of the amounts added. The absorption and the toxic effect 
of boron on plants varies with the variety of plants, the solu- 
bility of the boron compound, the amount of the boron compound 
added to the soil, the time elapsing after the compound is mixed 
with the soil before planting, the amount of rainfall, etc., and 
finally with the character of the soil to which the boron compound 
is added. 
THE JOURNAL OF BIOLOGICAL CHEMISTRY, VOL. XXXIII, NO. 3 
