348 MACDOUGAL AND SPOEHR— GROWTH AND IMBIBITION. 



A similar mixture of agar and urea (agar 90 parts, urea 10 

 parts) gave the following: 



Swelling. 



Water. HCl N/ioo. NaOH N/ioo. 



2173.0 per cent. 716.6 per cent. 560.2 per cent. 



Urea, the amino-acids, gelatine, albumen, and the saline soluble 

 proteins of the bean dissolved with agar and dried into thin plates 

 produced a greatly enhanced imbibition in water, an imbibition in 

 hundredth normal hydrochloric acid not more than a third of that in 

 water, while it was invariably less in alkaline than in acidified solu- 

 tions. The interest in swelling which begins with a neutral 

 desiccated section is however much less than that which attaches to 

 the behavior of such material under changing conditions of alkalinity 

 and acidity which are taken to occur in the living plant. 



Dried plates of agar-protein, agar-ty rosin and agar-cystin .12 

 to .25 mm. in thickness and 3 by 4 or 5 mm. were placed in trios 

 on the bottoms of stender dishes. Triangular pieces of glass were 

 placed to cover the sections of colloid in each dish and an auxograph 

 was arranged to give a bearing contact of the swinging arm on a 

 socket in the center of the triangular plate. So long as the prepara- 

 tion remained in this condition the pen of the instrument traced a 

 horizontal lin.e on the sheet carried by the drum. Dried sections 

 of the colloids have a very limited capacity for imbibition of acid 

 and alkaline solutions, and hence it was desirable to start swelling 

 or "growth" by an initial immersion of an hour in distilled water^ 

 which was poured in the dishes. After enlargement had begun 

 hundredth-normal acid or alkaline solutions were used in alternation 

 at intervals of one to three hours, as many as four changes being 

 made in some cases before the total swelling capacity was reached. 

 The results met all expectations based on theoretical considerations 

 and the auxographic tracings might easily be mistaken for records 

 of the variations of the length of a joint of Opuntia, for example. 



Sections of plates 90 parts agar to " 10 " of tyrosin gave a tracing 

 traversing 12 mm. vertically on the record paper during the first 

 hour immersed in distilled water, remained stationary making a 

 horizontal line during the second hour, the water having been 



