COLLOIDAL BEHAVIOR OF PLANT PROTOPLASM. 167 



The presence of any substance in the nucleus, chromosomes or 

 plasmatic bodies would give colloidal reactions materially different 

 from those to be expected when such substances are presented in 

 the cell sap or fluids according to the facts presented above. 



Maximum Effects Produced by Renewing Solutions. 



Closely related to the effects resulting by replacement of one so- 

 lution by another are those produced by renewing solutions. The 

 methods of auxographic measurement which have been used so ex- 

 tensively in these experiments entail the immersion of a trio of dried 

 sections of a total volume of about 4 to 8 cu. mm. in 25 to 30 cc. of 

 solution, the most common concentration of which was o.oi A^. The 

 procedure of drawing off this solution and replacing it with a fresh 

 solution at intervals of 12 or 24 hours has been followed since 191 8. 



It has been noted that at the first renewal made after the experi- 

 ment has been started an acceleration of the swelling would ensue 

 This speeding up has been attributed to two causes. First, as much 

 as 10 per cent, of the colloid may be drawn out into solution and the 

 presence of such a solution around the mass would operate to lessen 

 the rate of absorption of water by the more solid sections. Sec- 

 ondly, the ions of the substances in the hydrating solution pass into 

 the colloidal mass and enter into combination with the aggregates, 

 thereby lessening the concentration of the solution and consequently 

 its accelerating effect on hydration. The renewal of the solution 

 would remove the colloidal suspension about the sections and would 

 furnish a solution capable of exerting a hydrating effect equivalent 

 to the original, which would speed up the absorption of water.^ 



Usually these effects are shown during the first two or three 

 changes in swelHngs in which the total effect is practically finished in 

 ten days at 15° C. 



Dried sections of agar and a number of mixtures of agar and 

 gelatine are seen to show a much more pronounced and long con- 

 tinued reaction of this kind. The characteristic effect has been pro- 

 duced so far only by attenuated solutions of hydroxides of weak 

 metallic bases, by glycocoU and the basic glycocoll ester. 



5 MacDougal, D. T., and Spoehr, H. A., Bot. Gas., 69: (in press). 1920. 



