156 MEMOIRS OF THE NEW YORK BOTAXICAL GARDEN 



mentally to accelerate the germination of cereals, found that 

 when it was applied "as a manure" to wheat there is first a 

 stimulation, followed "on prolonged contact," by an injurious 

 effect. Ewart's conclusion was that the radioactive mineral 

 does not appear to have any direct agricultural value, at least so 

 far as wheat is concerned. 



Stoklasa^ exposed cultures of several nitrifying and denitrifying 

 bacteria in nutrient solutions to the emanation from pitchblend, 

 and from his results drew the inference that radioactivity exerts 

 a considerable influence upon the general circulation of nitrogen, 

 and is therefore important in connection with the fertility of the 

 soil. 



Malpeaux- studied the effect of a material "said to be radioac- 

 tive," on the growth of potatoes, sugar-beets, oats, turnips, and 

 rye. While the exposed plants were thought to be darker green 

 than the controls, and to have been slightly stimulated, the yields 

 were not appreciably greater than where an ordinary fertilizer 

 was used. An increase in the percentage of sugar in the beets 

 was thought to be due to the influence of the rays. 



In the same year Truffant^ studied the effect of growing various 

 legumes in soils containing radium bromide, but also rich in 

 nitrogenous and other mineral fertilizers. He reported that the 

 larger the content of the radioactive substance, the smaller was 

 the yield. Experiments with chrysanthemums grown in pots 

 led to the conclusion that radioactive minerals in the soil, both 

 soluble and insoluble, and especially the black oxide of uranium, 

 may produce favorable results, but that radioactive residues from 

 commercial factories may contain such deleterious substances as the 

 salts of barium and sulphuric acid in injurious amounts. Experi- 

 ments with spinach grown in the field gave no decisive results. 



Studies by Rusby* of the effect on crops of a substance claimed 

 by the Standard Chemical Company, of Pittsburgh, Pa., to be 

 radioactive led him to the conclusion that the substance, applied 

 as a manure, caused a substantial increase in the crop yield of 

 potatoes, radishes, celery, beans, cucumbers, tomatoes, egg plant, 

 carrots, beets, spinach, peas, pumpkins, cabbage, squash, clover, 



1 Compt. Rend. Acad. Sci. Paris 157: 879-882. 1913. 



= Vie Agr. ct Rur. 3: 289-293 1914. 



3 Jardinage, May, 1914. Agr. News, Barbados 13: 215. 1914. 



<J(nir. N. Y. B;jt. Card. 16: 1-23. Ja 1915. 



