THE TOXICITY TO FUNGI OF VARIOUS OILS AND SALTS. O 
cently reported the effect of about 50 different salts and acids upon 
yeasts, as compared with other organisms, and has found them gen- 
erally to be more resistant than algae or flowering plants. Silver 
nitrate, which is very deadly to many molds, bacteria, and alga? (the 
bacterium Staphylococcus pyogenes requiring only 0.0002 per cent to 
check growth; the alga?, Spirogyra and Cladophora, only 0.0001 per 
cent), will not kill yeast until the concentration reaches 0.001 per 
cent. Similarly, mercuric chlorid is toxic to Spirogyra in a 0.000001 
per cent solution, but a 0.01 per cent solution is required to kill beer 
yeast. 
Holds. — The common molds, such as Penicillium, Aspergillus, 
Sterigmatocystis, and others, taken as a whole, are highly resistant 
to toxic agents as compared with the true wood-destroying fungi. 
Whereas much experimental work has been done on the former, 
comparatively little has been carried out on the latter group. 
The so-called Penicillium glaucum Link., which in the light of 
recent work has been shown to consist of a group of several distinct 
species of Penicillium, to which the composite name was indiscrimi- 
nately applied, is one of the most resistant molds recorded. Pulst 
(23), Clark (3), and Gueguen (10) all agree that from 16 to 21 per 
cent of copper sulphate is required to stop its growth, and Pulst 
claims that it will even germinate and fruit in a 33 per cent solution 
of this salt or a 38 per cent solution of zinc sulphate if allowed to 
develop a sufficiently long time, i. e., from three to five months. 
Clark (3) has tested the effect of some 28 salts and acids upon four 
or five of the common molds, the tests being made in hanging drop 
cultures of beet infusion. His table of toxicities indicates that such 
salts as mercuric chlorid, potassium bichromate, silver nitrate, and 
potassium chromate are approximately 400 times as effective against 
these organisms as copper sulphate, sulphuric acid, hydrochloric 
acid, and zinc sulphate, the comparison being based on molecular 
solutions. 
EFFECT OF COMPOSITION OF MEDIUM ON TOXICITY. 
The toxicity of a substance may vary for the same organism when 
culture media of different compositions are employed. This is due, 
in large part, to the chemical or physical affinity of some substances 
for certain constituents of the media, or possibly to some change in the 
permeability of the plant protoplasm. The well-known reaction 
of some copper salts with sugars and of mercuric chlorid with albumi- 
nous compounds, or the effect of adsorption will serve to illustrate 
the point. 
The most careful work on toxicity has been conducted, using pure 
distilled water as a medium. However, the use of this method with 
fungi is practically limited to the germination of spores; nutrient 
