1915] 



MERRILL ELECTROLYTIC DETERMINATION OF EXOSMOSIS 567 



from plant roots, exosmosis from living cells, and of excretion 

 from leaves and other tissues. 



The methods of experimentation are described. 



A theoretical discussion is given of the various aspects of 

 the subject. 



The following are some of the experimental results ob- 

 tained : 



(a) Pea seedlings grew better in distilled water in which 

 exosmosis from the previously treated plants of the first crop 

 had occurred than in fresh distilled water, or in distilled water 

 in which untreated plants had been grown. 



(b) Peas and horse beans did not do as well in distilled 

 water in which pea seedlings had already grown for 21 days 

 as in fresh distilled water. 



(c) Abundant exosmosis may occur from treated plants, 

 even though the roots remain entirely normal in appearance. 

 When the tops were badly affected and the roots remained 

 normal, abundant exosmosis also occurred and the indications 

 pointed in some cases to a downward flow of substances into 

 the roots and out into the aqueous medium. No conclusive 

 proof of this was obtained, however. 



(d) Anesthetic vapors cause marked exosmosis upon con- 

 siderable exposure of the plants to them, but there is none if 

 the exposure be short. The interval required to initiate 

 exosmosis was accurately determined. The order of effec- 

 tiveness of the vapors tried is, ether, least ; illuminating gas, 

 more; and chloroform, most. 



(e) The time limits for the exposure of plants to extremes 

 of temperature in relation to exosmosis were determined. 

 Comparison was also made between the effect of dry and 

 moist heat. 



(f ) The exosmosis curves for various organic compounds 

 were found. In general, at the concentrations used, marked 

 excretion was produced. 



(g) The effects of single salts, salts in pairs, and salts plus 

 anesthetics in solution were ascertained as regards the exos- 

 mosis produced upon the plants in such solutions. Antag- 

 onistic relations in the sense of one substance decreasing the 



