340 MACDOUGAL AND SPOEHR— GROWTH AND IMBIBITION. 



As the plant did not show water relations which might be in- 

 terpreted as a direct combination of the separate action of gelatine 

 or agar, it was next proposed to test the reactions of a mixture in 

 which these substances would be blended, which was done in July, 

 1916. The first test mass was one consisting of about equal parts 

 of agar and gelatine, though the quantities were not weighed. Both 

 were soaked and melted separately and the gelatine was poured into 

 the hot agar which was kept at a temperature of about 90° C. for a 

 half hour. The mass was then poured onto a glass slab for cooling. 

 Two days later it was stripped off as a fairly clear and transparent 

 sheet slightly clouded, the average thickness of which was 0.2. mm. 

 Strips about 5X7 nim. were placed under the apices of sheet glass 

 triangles in glass dishes after the manner in which plant sections 

 had been tested, and auxographs were arranged to record the action 

 of acids, alkalies, and distilled water. This mixture gave swellings 

 as follows : 



Water. HCl N/ioo. NaO N/ioo. 



762.5 per cent. 687.5 per cent. 800 per cent. 



The mixture of these two substances having been found to 

 swell more in water and in alkaline solutions than in acid, a series 

 of varying proportions of the two constituents were made up. The 

 mixtures were poured inco moulds on glass plates and dried sheets 

 from .1 mm. to .6 mm. in thickness were obtained. The measure- 

 ments given below include the averages of tests under varied condi- 

 tions not only of thickness of the samples, but also of temperature, 

 length of period of swelling, tension of instruments, etc. The prin- 

 cipal results obtained were as follows : 



