250 RESEARCH SEMINAR. 



August 6. Theory of the Nature of Solutions. Dissociation 

 Hypothesis and Objections to It. By RODNEY H. TRUE. 



August 7. Toxic Action of Solutions on Plants Caused by 

 Solutions Containing One Solute. By RODNEY H. TRUE. 



August 10. Toxic Action of Solutions on Plants Caused by 

 Solutions Containing More than One Solute. By RODNEY 

 H. TRUE. 



August ii. Influence of Solutions on Plant Functions and 



Structure. By RODNEY H. TRUE. 



These seminars presented a discussion of the theory of elec- 

 trolytic association and its bearing on plant physiology. The 

 theory was outlined and some of the more recent objections to it 

 were stated, together with some of the more important grounds 

 on which such objections are based. Attention was called to the 

 bearing of these objections, with reference to physiological 

 research along these lines, and caution was advised in constru- 

 ing results in terms of the theory. It was pointed out that, as 

 long as a considerable mass of evidence lies against this hy- 

 pothesis, physiologists should not commit themselves too thor- 

 oughly to the theory and its conclusions. The toxic action 

 of various classes of compounds was then discussed in the light 

 of the dissociation hypothesis and the relation between physio- 

 logical action and molecular structure was pointed out. Some 

 relations obtaining between the structure and functions of plants 

 and the action of molecules and ions was discussed. 



August ii. The Influence of Insoluble Substances on the 

 Action of Poisons in Solution. By CHRISTOPHER S. OGLEVEE. 

 Seedlings of Lupinus a/bus were grown in beakers containing 

 the various poisons. The concentration which would kill the 

 radicle was determined. It was found that finely divided par- 

 ticles of an insoluble substance placed in the beaker containing 

 the poisonous solution not only allowed the radicle to grow, but 

 often accelerated the growth above the normal, and produced 

 effects similar to those of a more dilute solution. The insoluble 

 substances used, sand, pounded Bohemian glass, shredded filter 

 paper, potato starch, and paraffine, were cleaned and washed as 



