June 23, 1905.] 



SCIENCE. 



947 



some investigators have long claimed that 

 there are racial or specific differences be- 

 tween the organisms producing the tuber- 

 cles on the roots of certain leguminous 

 plants. From the results obtained by 

 Moore (in the U. S. Department of Agri- 

 culture) which have been reported, but not 

 yet published, I am permitted to recite a 

 further interesting fact of accommodation. 

 AVhen an organism isolated from one host 

 species is grown for a time artificially, un- 

 der special conditions of nutrition, its 

 host limitations are in great measure broken 

 down, and it may produce tubercles on a 

 variety of leguminous plants. It is like- 

 wise conceivable that in the case of certain 

 yeasts the temperatures at which spores are 

 formed, and the specific fermentative ac- 

 tivities, may be changed by special condi- 

 tions of cultivation. 



In view, therefore, of the work already 

 accomplished it is certainly evident that 

 the propriety of basing what are termed 

 species upon certain physiological char- 

 acters has distinct limitations. I do not 

 intend to bring into this paper a discussion 

 of the inadequacy of the present nomen- 

 clature system from a physiological point 

 of view. It may be said, however, that it 

 is scarcely possible for the systematist to 

 consider all physiological characteristics, 

 or to appreciate the confused ideals of the 

 physiologist. 



Stimulated by the marked advancement 

 which has been made in physical chemistry, 

 especially in the knowledge of electrolytic 

 dissociation, the past few years have added 

 much to our fund of information with rela- 

 tion to the toxic action upon plants of solu- 

 tions of both acids and salts, as well also as 

 of certain non-electrolytes. The work of 

 Kahlenberg and True, Heald, Kronig and 

 Paul, Clark and others has contributed 

 enough data for an appreciation of the 

 limitations of toxic action. Nevertheless, 



no broad generalizations are as yet possible. 

 Indeed, it is not generalizations which are 

 wanted, but further experimental data 

 bearing upon the relation to the toxicity of 

 the ions and molecules and their respective 

 interactions. 



Studies may well be made dealing with 

 the relation of nutrition to toxic agents, 

 the effects of temperature and other condi- 

 tions upon such action, and the accommoda- 

 tion of organisms to increasing strengths 

 of deleterious agents. Naegeli's work on 

 the oligo-dynamic action of copper is be- 

 ginning to be appreciated and in one way 

 or another the results have in recent times 

 been repeatedly confirmed. In most cases, 

 however, no allowance has been made for 

 the action of the nutrient salts which may 

 be present in the culture fluid and which 

 may affect in a very dissimilar way two 

 different electrolytes. In this connection 

 it is only necessary to call attention to the 

 toxic action of certain compounds of mer- 

 cury, in which increased toxicity, due to 

 the presence of small amounts of some other 

 salt of the same acid as the mercury salt 

 used, is indeed quite remarkable. Within 

 the past few months an unusually interest- 

 ing paper has appeared in which Kanda 

 reports the action of certain toxic agents 

 upon plants grown in pots as compared 

 with those plants grown in water cultures. 

 His important conclusions are as follows: 



( 1 ) A strongly dilute copper sulphate solu- 

 tion, even 0.000,000,249 per cent., is injuri- 

 ous to seedlings of the common garden pea 

 in water cultures ; and neither a solution 

 ten times nor one a hundred times more 

 dilute produced any stimulative effect. 



(2) In pot experiments with soil, the same 

 seedlings are uninjured when watered 

 twice a week during a period of from five 

 to eight weeks with a solution of .249 per 

 cent. ; in other words, even after from five 

 to seven grams of copper sulphate were 



