418 BOTANICAL GAZETTE [MAY 
that used and fully described by CLARK. Hawkins finds in general that the 
addition of the nitrates of calcium, magnesium, and potassium to solutions of 
nitrates of copper, lead, or zinc reduces the toxicity of the solutions. With 
potentiometer measurements of the concentration of copper ions in the mixture, 
that neither the reduction of the degree of ionization brought about by the 
mixing of the salts nor the formation of double salts will account for the lower- 
ing of the toxicity of the copper solution by the addition of the calcium salt. 
For combinations of lead nitrate with nitrates of calcium and magnesium, it 
is shown that reduction in ionization cannot account for the reduced toxicity 
of the lead salt. For lead nitrate and zinc nitrate within the limited range of 
concentrations used (3) there is a constant ratio between the molecular con- 
centration of the toxic salt and that of the antitoxic salt. necessary to inhibit 
the action of increasing concentrations of the toxic salt. For the combination 
of copper nitrate with calcium nitrate no such constant ratio was evident. 
The author concludes that the antagonistic action of one salt upon another 
cannot be attributed, as some investigators have done, either to reduction 
of the dissociation of the toxic salt or to the formation of undissociated double 
ts. 
Incidental to an investigation, the object of which was to determine the 
factors inducing the formation of giant cells and mucor yeast by the mucors, 
Ritter” has reported a few experiments on the influence of nitrogenous com- 
pas and sodium chloride on the toxicity of acids. The inhibition of 
germination of the spores was taken as a criterion of toxicity, although some 
ty was experienced with this test because many of the mucor spores 
began to form giant cells in concentrations of acid far below the toxic limit. 
The culture solutions contained, in addition to potassium di-hydrogen phos- 
phate and magnesium sulphate, either peptone or ammonium nitrate and sugar. 
It was found that malic, citric, tartaric, nitric, and hydrochloric vie vere 
much less toxic in the peptone medium than in the ammonium nitra 
The author generalizes from these observations to the effect that he toxicity 
of organic and inorganic acids is increased by the presence of inorganic nitro 
gen and depressed by organic nitrogen compounds. The data, it should . 
remarked, do indeed show an increased toxicity of acids in the presence of 
ammonium salts as compared with organic nitrogen compounds, but no data 
showing an absolute increase of toxicity asa result of the addition of ammonium 
*6 Ritter, G. C., Die giftige und formative Wirkung der Saéuren auf die Mucora- 
ceen und ihre Beziehung zur Mucorhefebildung. Jahrb. Wiss. Bot. 52:351~493- 
MM. 3. 20T%: 
