4 BULLETIN 1316, U. S. DEPARTMENT OF AGRICULTURE 
causes of death of orchard trees in the West, producing symptoms 
similar to those caused by arsenic. Grossenbacher (21) states that 
Headden's conclusions were unwarranted. However, work by 
Swingle and Morris (43) in Montana and later by Hotson (30) in 
Washington demonstrates that even the relatively insoluble arseni- 
cals 'used in orchard sprays are capable of producing cankers which 
may develop into typical crown-rot in apple trees. They conclude 
that crown-rot is a condition which may be brought about by any 
one of a number of causes working together or separately and that 
arsenic poisoning undoubtedly plays a part in some of the cases. 
From the work of Jadin and Astrug (32), who found small 
quantities of arsenic in 85 species of plants representing 30 families 
of flowering plants and mushrooms growing naturally and in healthy 
condition, it appears that Headden may have overemphasized the 
danger to plant growth from small amounts of arsenic in soil. 
Ampola and Tommasi (1) report that in nutrient solution it re- 
quired 1 milligram of arsenic per liter of water to injure agricul- 
tural plants, whereas in soils growth was checked at concentrations 
corresponding to 0.3 milligram of arsenic per kilogram of soil. 
Voelcker (45) found that 0.02 per cent of soluble arsenic, such as 
sodium arsenite, when applied to soils in pot cultures caused crop 
failures; 0.05 per cent retarded germination of seeds; and 0.01 per 
cent, representing 825 pounds of arsenic acid per acre, had no ill 
effects on plants. 
Gosio (12), working on the problem of accumulation of arsenic in 
plants, found arsenic noninjurious at low concentrations. He grew 
squash plants in boxes of soil and watered them with arsenical water, 
using a solution of 1 part of metallic arsenic to 1,000,000 parts of 
water, one month later changing to 1 to 100,000 and two months later 
increasing the concentration to 1 to 10,000 until maturity. The 
squash fruits contained 0.0041 per cent of arsenic and apparently 
were in good condition. 
Brenchley (9) gives results of careful experimentation with arseni- 
ous acid added to soil in pot experiments. Adding the arsenic to 
the soil before seeding with barley, wheat, rye, and maize, 0.10 per 
cent of arsenious acid had no effect on the germination of barley, 
wheat, and rye, and maize withstood 0.40 per cent concentration 
without retarding germination. A concentration of 0.8 per cent was 
strongly adverse to germination of all plants tested. Growth was 
affected b}^ 0.10 per cent concentration and in case of barley even 
by 0.05 per cent concentration. Eye proved more resistant than 
wheat. The results obtained by Wober (48) agree with the above as 
to the order of susceptibilit}^ of plants. He studied the effects of 
smelter emanations containing arsenic on economic plants and placed 
them in the following order as to susceptibility: Legumes, barley, 
oats, wheat, maize, and rye. 
The results obtained by Guthrie and Helms (22) on the limits of 
endurance of arsenic by certain plants run parallel to those of 
Wober. In cultures in galvanized-iron pots the growth of barley 
was affected by 0.05 per cent concentration of arsenious acid, and 
growth was prevented by 0/10 per cent concentration. The germina- 
tion of rye was affected by 0.20 per cent concentration, growth 
affected by 0.15 per cent, and growth prevented by 0.30 per cent. 
