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PACIFIC SCIENCE, Vol. I, July, 1947 
ing, one corrosive, one systemic, and one which 
was an arsenic-lime poisoning. He pointed out 
that arsenical deposits in the soil are for the most 
part insoluble, but warned that the soluble frac¬ 
tions had already passed the danger limits in cer¬ 
tain areas. He recognized that absorption of arse¬ 
nic by the roots takes place. He further pointed 
out that salts such as NaCl, Na 2 S0 4 , and Na 2 C0 3 
are all capable of making lead arsenate soluble in 
the soil solution and that lime salts do not prevent 
the solution of arsenates. 
Headden was joined in his efforts by Swingle 
and Morris (1911), who reported that serious in¬ 
jury may result to apple trees from the applica¬ 
tion of insoluble arsenicals and that recent wounds 
through the outer bark, functional lenticels, and 
dormant buds permit the absorption of arsenic in 
solution. 
Greaves (1913) observed that water-soluble 
arsenic may exist in soils to the extent of 82 ppm 
without entirely stopping ammonification and ni¬ 
trification. He considered it improbable that lead 
arsenate, zinc arsenite, or arsenic trisulfide would 
ever be applied to agricultural soil in quantities 
sufficient to'be injurious to soil bacteria. 
Greaves and Anderson (1915) reported actual 
stimulation of soil flora by soluble arsenic in soil 
at 10 ppm. Toxicity began at 40 ppm and nitrogen 
fixation was entirely stopped at 250 ppm. The 
quantity of 10 ppm which they reported as causing 
stimulation exceeds that found in most soils, and 
they concluded that arsenic will stimulate instead 
of retard bacterial activities of soil. Greaves 
(1916) reported that arsenic cannot replace phos¬ 
phorus in the vital process of nitrogen fixing, but 
it can, in some manner, liberate phosphorus from 
its insoluble compounds. 
Swingle (1920) investigated the effect of arsenic 
on species of soil bacteria responsible for impor¬ 
tant chemical changes such as ammonification and 
nitrogen fixation. Contrary to the work of Greaves, 
Swingle’s results showed that all the arsenical 
compounds used were germicidal, but in different 
degrees. 
Green and Kestell (1919) found bacteria which 
are resistant to arsenic to be infrequent in soil and 
air, but fairly frequent in feces. Of the twelve or 
more resistant species examined, only two showed 
any chemical activity toward arsenic: one, which 
oxidizes arsenite to arsenate, and another, which 
reduces arsenate to arsenite. No relationship was 
discovered between arsenate reduction and nitrate 
reduction. 
McGeorge (1915^; 1915£) appears to have been 
the first in Hawaii to recognize the possible dele¬ 
terious effects which may result from the use of 
sodium arsenite as a herbicide, a practice then 
coming into general use in the Territory. His re¬ 
searches involved a study of the effect of sodium 
arsenite on the growth of millet, cowpeas, and 
buckwheat and on the physical, chemical, and bio¬ 
logical activities in heavy red clay, brown clay, 
and highly organic silt soils. He found that the 
effect of sodium arsenite on plant growth depends 
upon the resisting power of the plant and upon 
the chemical and physical nature of the soil. In 
small quantities, the compound stimulated plant 
growth in most instances, but when added at the 
rate of 0.1 to 0.25 per cent, it made plant growth 
virtually impossible. 
Sodium arsenite, he discovered, materially al¬ 
tered the mechanical condition of the soil, its ac¬ 
tion being primarily that of a deflocculating agent 
checking the movement of water. 
Sodium arsenite, McGeorge showed, was 
strongly fixed by the soil, even resisting the wash¬ 
ing of heavy rains. An analysis of a sample of 
soil from a tract of land sprayed three times a 
year for 5 years, at the rate of 5 pounds of sodium 
arsenite per acre per application, showed all the 
arsenic to be present in the top 4 inches of soil. 
The fixation of arsenites by the soil involved 
chemical reactions consisting of replacement of 
solution of iron, calcium, magnesium, and humus, 
owing in part to a hydrolysis of the sodium arse¬ 
nite in solution and in part to a combination with 
the dibasic and tribasic elements, to form the rela¬ 
tively insoluble arsenites and arsenates. 
Brenchley (1914^; 1914£) distinguished be¬ 
tween higher and lower forms of plant life in 
their reactions to arsenic. In certain algae, stimu¬ 
lation may result from the presence of arsenic 
compounds. Some fungi apparently are able to 
live in the presence of arsenical compounds. On 
higher plants, the toxic effect of arsenic was found 
much more marked with arsenious acid and its 
compounds than with arsenic acid and its deriva¬ 
tives. Using peas and barley, she could observe no 
stimulation even with the smallest quantities used. 
Morris and Swingle (1927) reported that the 
addition of small amounts of soluble arsenical 
compounds to potted plants caused serious injury 
to most of the plants under test. The authors con¬ 
cluded that the incorporation of arsenical com¬ 
pounds in the soil is a dangerous practice, and 
may cause considerable injury as the concentra¬ 
tion increases. They further concluded that beans 
and cucumbers were very susceptible, whereas 
cereals and grasses were more resistant. 
To judge from the material so far presented, it 
appears that the use of arsenic has several prob¬ 
lems associated with it. The preponderance of 
opinion is that arsenic is harmful to higher plants 
but that when the arsenic occurs in very small 
concentrations, it may cause some stimulation. 
Contrary opinion on the latter point is, however, 
rather substantial. The stimulating effect of arsenic 
on algae and fungi seems not uncommon, but its 
favorable influence on soil organisms regarded as 
useful to agriculture is at least questionable. While 
the argument was going along on these somewhat 
academic lines, great quantities of arsenic were 
