

^82 BOTANICAL GAZETTE [may 



o 



temperature upon the process of diffusion is such that Q I0 is approx- 

 imately 1.3. Applying the results of these experiments to this 

 case it is found that the coefficient obtained does not correspond 

 with either the van't Hoff coefficient or the diffusion coefficient. 

 Measurements of the permeability of membranes made heretofore 

 have shown in general a temperature coefficient approximating 

 that of the van't Hoff law, but there is no evidence in these experi- 



■ 



ments that in the passage of water through the seed coat of the 

 peanut chemical processes are exclusively involved. Apparently 

 also the effect of temperature is not merely upon the rate of diffusion 

 of water. Probably we are not justified in using the numerical 

 coefficients obtained to form any conclusion as to the nature of the 

 process by which water passes through the peanut membrane. 



Comparison with temperature coefficients obtained by others. — 

 Krabbe (19) measured the effect of temperature upon the per- 

 meability of the living cells of cylinders of pith of Helianthus annuus 

 and pieces of roots of Vicia Faba, etc. As criteria he took the rate 

 of increase in length of pieces of plasmolysed tissue, allowed to 

 absorb water at temperatures in vicinity of o° and 20 C, and the 

 length of time for plasmolysis to occur at these temperatures. He 

 found that the velocity of water movement increased 3-5 times 

 when the temperature was increased 20 C. (Q J0 approximately 

 2.0-2.5). He believed that this high coefficient indicated that 

 purely physical forces were not operative, but that it was due to 

 a specific property of living protoplasm. 



Rysselberghe (26) investigated the effect of temperature upon 

 the permeability of the living protoplasm, using pith cells of Sam- 

 bncus nigra, lower epidermal cells of Tradescantia, and filaments of 

 Spirogyra. He made use of 3 methods: the rate of shortening 

 of a tissue in a plasmolysing solution at different temperatures, 

 the rate of elongation of plasmolysed tissue in water at different 

 temperatures, and the rate of plasmolysis of a tissue under micro- 

 scopic observation. His general results are as follows: 



Temperature 06 12 16 20 25 3° 



Comparative rate ....i 2 4.5 6 7 7.5 8 



This gives an average value for Q I0 from o°-30° of 2.0. Ryssel- 

 berghe does not agree with Krabbe that this high coefficient 

 necessarily indicated the special activity of vital matter. 



