MISCELLANEOUS 



415 



3\0 I 4.|0 I 5|3 ' dp ' 7.\o ' 3^ ' ?lo /"/y 



Apple Tissue - Thin Slices 

 I Hour 



J • 



■H • 



♦— — — — • 



• 5=5. 



Cor/7 Seeds - /Mr Dry 

 l/l- Hrs. 



Corn - Seed Powder 



Monilia Sitophilia 

 "* l^at of H\/phae - >? Mrs. 



^ t g U ^ Potato Tuber -Thin Slices 



I 4- /yr5. 



4 /Vr5. 



_, Potato Tuber 

 Thin Slices 



3 Hrs. 



Rye Seeds 



■• /I/r Dry - 3 Hrs. 



Wheat Seeds 



"• /J/V- Dry -5 Hrs. 



Potato Roots 

 3 Hrs. 



_, Bar/ey Roots 

 3/2 Hrs. 



3\0 I 4|0 .1 5\0 I 6\0 I 7|0 



8\0 



9.\0 pH 



Figure 166. The relation between the pH equilibrium of tissues in a series of buffers 

 and the pH of the water extracts of these tissues. The arrows show the pH of the buffer 

 in which the sample of tissue was placed, the direction of change in pH, and the final 

 pH attained. The vertical lines show the pH of the water extracts of the tissues. It 

 is seen that the isoelectric point of the tissue as determined by this method coincides 

 with the pH of the water extract in all tissues except in the case of corn seeds, air-dry 

 whole seeds. 



substances with isoelectric points, nor that these substances are not of 

 great importance in the Ufe processes of plants. Nor do we claim to have 

 shown that the tissue itself does not have an isoelectric point. Robbins and 

 his co-workers have brought evidence by other methods of experimentation 

 (water absorption, toxicity of ions, staining of tissues, etc.) regarding the 

 existence of such a point. 



"Our objection is mainly to the method of determining tissue isoelectric 

 points by immersing the tissue in a series of buffers and assuming that the 



