COLLOIDAL BEHAVIOR OF PLANT PROTOPLASM. 



159 



drogen ions, and their growth would be markedly limited by acidity. 

 Such mixtures would also be modified something less by hydroxy! 

 ions. All types of biocolloid would respond by increased hydration 

 to the presence of amino acids as shown by the relative swellings in 

 glycocoll and in histidine. 



The results with the basic histidine and of its salt histidine dihy- 

 drochloride, which reacts as an acid, are as given in Table III. 



TABLE in. 



Swellings of Agar, Gelatine and Mixtures in Percentages of Original 



Thickness and Volume. 



Mixtures consisting of 40 to 60 per cent, of the two main com- 

 ponents are seen to give the highest swelling values in histidine yet 

 obtained by biocolloids by treatment with any reagent. Further- 

 more this amino-compound acts to increase the sw^elling of gelatine 

 and all mixtures containing it to a point beyond that which is pos- 

 sible in water. Its acid salt has the well-known effect on agar, gela- 

 tine and their mixtures. These features are illustrated by Table IV. 

 in which the values are given in terms of water as 100. 



In addition to the high hydration caused in the above mixtures 

 by histidine, attention has been previously called to a similar action 



