126 J. F. MCCLENDOX. 



in less concentration, and probably affect the cell chemically 

 as well as physically. 



Mineral acids caused exosmosis of tannin when the concen- 

 tration just exceeded 1/6,400 normal, and the effect is probably 

 due to H ions. At this same concentration Kahlenberg and True 1 

 found the growth of seedlings of Lupinus albns to cease. It 

 appears, therefore, that this cessation of growth is due to in- 

 creased permeability, causing decreased turgor of the cells. 



Changes in permeability may also affect secretion (excretion). 

 The addition or formation of alcohol or acetates causes yeast and 

 other fungi to secrete (excrete) for a short time, various sub- 

 stances, especially enzymes which do not come out in a culture 

 medium lacking the reagent. 2 It appears that the alcohol or 

 acetates increase the permeability of the fungi to these substances. 



My own experiments 3 indicate that pure MgClo solutions 

 increase the permeability of yeast. A certain per cent, of yeast 

 and dextrose in .3 molecular MgClo eliminated CO 2 more rapidly 

 than .$M NaCl or .^2^M CaCl 2 , all which have about the same 

 freezing points. Also, the CO 2 elimination was more rapid in 

 the magnesium solution than in a solution of the same concen- 

 tration of MgCl 2 with either of the other salts in addition, or in a 

 solution containing NaCl and CaCl 2 in the same concentrations 

 as in their respective pure solutions, or in a solution of all three 

 salts, or in tap or distilled water. In order to determine whether 

 the magnesium entered the cells I took two equal masses of com- 

 pressed yeast and agitated one in H 2 O and the other in a molecular 

 solution of MgCl 2 for 5 hours, i-hen washed each rapidly in H 2 O 

 by means of the centrifuge. The ash of the magnesium culture 

 = .048 gram, that of the control = .0466 gram. Evidently 

 the Mg did not enter the yeast to any great extent, and probably 

 acted on the surface, increasing the permeability. 



Ewart 4 observed that after placing plant tissue in 2 per cent. 

 HC1 and washing in water its electric conductivity (ionic per- 

 meability) was increased. If one portion of the plant is stimu- 

 lated, the stimulus may be transmitted to other portions. ' In 



1 Kahlenberg and True, Botanical Gazette, 1896, XXII., p. Si. 



2 Zangger, "Asher and Spiro's Ergcb. d. Physiol.," 1908. VII., 144. 

 McClendon, Am. Jour. Physiol.. 1910, XXVII., p. 265. 



4 " Protoplasmic Streaming in Plants," Oxford, 1903, p. 96. 



