tology. To our knowledge the medical profession has not followed up
the possibilities which this substance offers. The author is familiar
with one case in which pure juglone was applied to a persistent ringworm
infection. The infection disappeared within a month after treatment was
begun. Though conclusions can not be drawn on a single case, certainly
this observation lends credence to the medicinal lore of the ancients
and the American pioneers.

During the fall and winter of 1942-43, investigations on juglone were
started at the Connecticut Agricultural Experiment Station in
conjunction with studies of the effect of other plant toxins on the
roots of higher plants. When the toxicity of this oxidizing compound was
established, it was produced in some quantity both by extraction from
walnuts after the method of Combes (1907) and by synthesis after the
method of Bernthsen and Semper (1887). Working on the assumption that
the killing of germinating fungus spores and root hairs are similar
phenomena, juglone was subjected to standardized laboratory tests for
fungicidal value. In a series of experiments, this compound proved to be
equally toxic with the copper in Bordeaux mixture. Such a high degree of
toxicity was deemed worth further investigation, so juglone was tested
as a seed protectant and as a spray in field trials for the control of
black spot of roses.

As a seed protectant, juglone failed miserably. It's toxicity to the
noncutinized surfaces of root tissues was so great that germination was
abnormal and greatly impaired. The injury noted here was apparently the
same as that discussed by Brown (1943) and that which occurs normally in
the field.

In field tests on the control of black spot of roses juglone stood up
well. No phytotoxic activity could be noted on the cutinized stem and
leaf surfaces. On the variety George Ahrens, juglone gave equal control
with 2-1/2 times as much 325 mesh sulfur, the standard control for this
disease.

SUMMARY

1. Under certain conditions walnut trees exhibit toxicity to those
plants whose roots are in intimate contact with the roots of the walnut.

2. This toxicity is due to the action of juglone, the oxidized form of
hydrojuglone, a non-toxic substance occurring in the inner bark and
green husk of walnuts.

3. Juglone has been used in dermatology to cure various skin disorders
including both bacterial and fungus diseases.

4. As a seed protectant, juglone is unsuitable