542 MACDOUGAL AND SPOEHR— GROWTH AND IMBIBITION. 



Gelatine. '■ 



Water. HCl N/ioo. HCl N/ioo+NaCl N/ioo. 



616.7 per cent. 1016.7 per cent. 833.3 per cent. 



466.7 1083.3 1083.3 



1 133-3 883.3 ' 



866.7 



833-3 



Averages: 483.3 1077.8 899.9 



The superior swelling of gelatine in acidified solutions is illus- 

 trated and a lower average of swelling in hundredth normal hydro- 

 chloric acid in the presence of a salt solution of the same concen- 

 tration was demonstrated. The admixture of hundredth normal 

 -acid and of hundredth normal salt solution gives a solution of two 

 ^hundredths normal concentration. Gelatine shows a lesser swelling 

 in this weaker acid, and furthermore the presence of the salt appears 

 to increase imbibition. 



Sugars are an important constituent of living tissues and it is 

 highly probable that in addition to pentose, sucrose and dextrose 

 are also in the colloidal suspensions of the protoplast. It was im- 

 portant to determine whether or not they exerted any direct effect 

 in the concentrations in which they might occur in the cell. A series 

 of tests of the effects of these substances was carried out by Mr. E. 

 E. Free at the Coastal Laboratory in September, 191 6. Gelatine 

 and agar were mixed in various proportions, dried to thin sheets 

 and then swelled at temperatures of 16 to 21° C. 



Sugar solutions of a concentration less than 25 per cent, did not 

 •dift'er appreciably in its effects from distilled w-ater. Sucrose con- 

 centrations of a 50 per cent, concentration produced a markedly 

 lessened concentration of all gels. Dextrose of the same strength 



