Livingston : Chemical stimulation of a green alga 31 



and Heald * worked upon Lupinus, Pisum and Zea radicles, 

 finding an acceleration in case of the cations H, Cu, Ni, Co and 

 Ag. Kahlenberg and Austin f determined the concentration of 

 ionic H which can be borne by seedlings of Lupinus when their 

 roots are in solutions of acid sodium salts. Coupin % made 

 determinations of the effect of solutions of salts of Na, K, and NH 4 

 upon wheat seedlings. Kanda § worked with Pismu and Vicia 

 seedlings and with CuS0 4 and ZnSO r Studies on the toxicity 

 of a number of acids and their Ca and K salts upon wheat, clover, 

 and maize, were made by Cameron and Breazeale.|| True and 

 Gies t have recently carried out what is probably now the most satis- 

 factory research we have on this subject. They determined for 

 Lupinus the stimulating strengths and fatal concentrations for the 

 salts of Cu, Ag, Hg, Zn, Na, K, Ca and Mg. F. A. Loew** worked 

 upon the effect of H and OH ions on Zea seedlings, and Dandenoff 

 has just published a paper on experiments in this line with seedlings 

 of Zea, Lupinus, and Pisum. The latter author made determina- 

 tions of the neutralizing power of seedling roots in toxic solutions, 

 which appears to be a very important consideration and one which 

 seems not to have been attacked before. This author demon- 

 strates also, what had already been described by True and 

 Oglevee|| that the presence of insoluble bodies has an influence 

 upon the physiological effect of salt solutions. This is the phe- 



* Heald, F. de F. On the toxic effect of dilute solutions of acids and salts upon 

 plants. Bot. Gaz. 22 : 125-153. 1896. 



f Kahlenberg, L. & Austin, R. W. The action of acid sodium salts on Lupinus 

 albus. Jour. Phys. Chem. 4 : 553-569. 1900. 



% Coupin, H. Sur la toxicite des composes du sodium, du potassium, et de l'am- 

 monium a l'egard des vegetaux superieurs. Rev. Gen. Bot. 12 : 1 77-194. icoo. 



\ Kanda, M. Studien iiber die Reizwirkung einiger Metallsalze auf das Wachs- 

 thum hoherer Pflanzen. Jour. Coll. Sci. Imp. Univ. Tokyo 19 13 : 1-37. 1904. 



|| Cameron, F. K. & Breazeale, J. F. The toxic action of acids and salts on 

 seedlings. Jour. Phys. Chem. 8 : I-13. 1904. 



TJTrue, R. H. & Gies, W. J. On the physiological action of some of the heavy 

 metals in mixed solutions. Bull. Torrey Club 30 : 390-402. 1903. 



**Loew, F. A. The toxic effect of H and OH ions on seedlings of Indian corn. 

 Science II. 18 : 304-308. 1903. 



ft Dandeno, J. B. The relation of mass action and physical affinity to toxicity. 

 Am. Jour. Sci. IV. 17 : 437-458. 1904. 



%% True, R. H. & Oglevee, C. S. The effect of the presence of insoluble sub- 

 stances on the toxic action of poisons. Science II. 19 : 421-424. 1904. — Also Bot. 

 Gaz. 39 : 1 -2 1. 1905. 



