136 



BOTANICAL GAZETTE 





[august 





assumes a special interest, as the total swelling in water is greatest 

 of all of the combinations, and the depressing effects of acid, 

 hydroxide, and salt are very marked. These features would be 

 characteristic of a plant capable of a wide range of water content 

 and sensitive to changes in the sap, as is known to be the case 

 from studies of the growth of Opuntia. 



The substitution of gelatine for albumin, or its addition to a 

 mixture increases swelling in acid, salt, and hydroxide as would 

 be expected, and lessens the total swelling in water. These and 

 other available data may be profitably construed in many direc- 

 tions in the interpretation of growth phenomena. 



The methods of preparation and measurement of swelling of 

 . colloids described have served to confirm and extend knowledge 

 of the behavior of agar, albumin, gelatine, and of mucilages, and 

 to fix upon pentosan-protein mixtures which swell in a manner 

 similar to cell masses of plants. The use of the auxograph has 

 made it possible to compare the nature, extent, and duration of 

 these changes with variations in volume of growing cell masses. 



The casting and desiccation of colloidal plates in such manner 

 that shrinkage and swelling takes place unequally in different 

 axes, and the measurement of such differential swelling also fur- 

 nishes some evidence which may be of value in interpreting the 

 changes in form, etc., of the special bodies of the protoplast which 

 accompany and mark the morphological crises of the cell. 



Desert Laboratory 

 Tucson, Ariz. 



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