EFFECT OF THALLIUM ON PLANT GROWTH 3 
as a food for man. Certain samples of commercial asparagine 
contained thallium. 
The effect of thallium compounds on the germination of seeds and 
the growth of plants in pot cultures has been reported (9, 13, 15, 
16, 20). Germination or growth of the seed of Lepidium satiwum 
was completely prevented by 340 parts of Tl per million (9). Seed- 
lings of Vicia faba, Lupinus albus, and Zea mays showed slight growth 
but died in2to4days. Practically all the thallium had been resorbed 
from solution in 24 to 72 hours. In the same concentration in Shive’s 
solution, plants exposed to thallium compounds grew nearly as well 
as the checks, and the thallium concentration was unchanged during 
10 days. There was no relation between the quantity of thallium 
present and the development of the root surface. Equimolar solu- 
tions of cadmium nitrate, chloride, or sulphate were more toxic than 
thallium solutions (20). In solution or pot cultures certain con- 
centrations of thallium salts produced symptoms resembling ‘‘french- 
ing’’ in tobacco plants. In many instances the stem was killed at the 
surface of the soil. This was attributed to the direct application of 
the solution, which was not leached to any considerable extent from 
the surface layers (16). The growth of wheat, buckwheat, alfalfa, 
rye, and soybean plants was slightly retarded by 1.5 to 7 parts of 
Tl per million (table 1). Wax beans were somewhat more resistant. 
The injury was greatest in sandy loam soil. Leaching did not pre- 
vent the harmful action that appeared to be associated with an 
alteration in the base equilibrium, with the liberation of aluminum 
and calcium (18). 
Perhaps the most striking results in studies of the toxicity of various 
metallic salts to seedlings have been attained with copper sulphate. 
These results are of special interest because of the wide-spread use of 
copper compounds as fungicides. Kanda (/1) reported that 
0.000,000,0249 percent solutions of copper sulphate (a concentra- 
tion of 1 in 4,000,000,000) definitely checked the growth of seedlings 
of peas, broadbeans, and buckwheat. No comparable studies on 
thalium compounds were reported by him, but this would suggest 
that copper is several hundred thousand times as poisonous to the 
growth of plant seedlings as is thallium. 
Brooks (4, p. 106) stated that a bait containing 0.5 g of thallous 
sulphate was suspended on stakes a few inches above the grassy slope 
in an arboretum in the Hawaii Sugar Planters’ Association in July 
1929. In July 1931 there was a patch of bare earth 1 to 3 feet long 
and perhaps one-third as wide. 
Not a single trace of plant life was or had been apparent on these areas during 
the intervening 2 years * * *. One bait, containing 0.5 gm of TlSQOu,, 
would under average conditions sterilize not less than half a cubic foot of soil. 
He concluded: Continued scattering of thallium sulphate baits will 
presumably lead to: ‘‘(a@) complete denudation of numerous small 
areas of pasture or range land * * * (6) General toxicity or 
complete sterility of cultivated land * * *.” This was so 
greatly at variance with the writers’ observations in California and 
elsewhere, where thalgrain (grain coated with 1 pound of thallous 
sulphate per 100 pounds) has been exposed, that contact was estab- 
lished with the Hawaiian authorities to learn more about. this. 
