60 Hydration and Growth. 



first and 2 of the last, coming down to a thickness of 0.22 to 0.23 mm. 

 These swelled at 17 C. to the proportions shown in table 45, which in 

 some cases exceeded that in water. The swelling in concentrations as 

 high as 0.01 M were but little below that in water. 



Glycocoll has been used in many cultural tests with plants and 

 various interpretations have been placed on its accelerative influence 

 on growth. The experiments with this material, therefore, included 

 the possibilities of the manner and extent to which this might accom- 

 pany or run parallel with hydration reactions. 



The first trials were made with this reagent incorporated with 

 liquid agar in such proportion that the amount present in three sec- 

 tions would have been equivalent to that in 30 c.c. of 0.14 M solution. 

 Trios of such sections 0.15 mm. thick gave swellings of 1,133, 1,267 

 and 1,300 per cent hi water at 16 C., which is much less than that 

 shown in a solution at 0.3 M containing twice as much of the amino- 

 acid. (Table 45). 



Thin sections of agar swelled in all glycocoll solutions less concen- 

 trated than 0.3 M to the amplitude attained in water and exceeded it in 

 some cases, a fact which for the first time gives a sound basis for cul- 

 tural tests in which growth was accelerated and the total increased by 

 this compound. 



Another pentosan, gum tragacanth, was dried from solutions to form 

 sections 0.13 mm. thick on filter-paper. Swellings at 15 C. were ob- 

 tained, as shown in table 48. 



TABLE 48. p. ct. 



Distilled water 1 ,380 



Glycocoll, 0.03M 1,382 



Glycocoll, 0.05M < 1,077 



Glycocoll, 0.01 M 1,462 



This gum liquefies irregularly, and hence the figures show the extent 

 of swelling before active dispersion of the mass begins. 



A mixture of 9 parts gelatine and 1 part gum tragacanth was made 

 up at 25 per cent to correspond to a similar mixture of gelatine and 

 opuntia mucilage. Swellings as follows at 15C. were obtained: 



TABLE 49. p. ct. 



Distilled water 1,320 



Glycocoll, 3 M 1,520 



Glycocoll, 0.05M 1,040 



Glycocoll, 0.01 M 1,320 



Nothing may be concluded on the basis of these figures, except that 

 the hydration of this material reaches a stage where it goes into dis- 

 persion unevenly and in a manner which makes auxographic readings, 

 as well as all mass or weight determination, of doubtful value. 



The above tests were repeated with opuntia mucilage at 15 C., 

 with results as shown in table 50. 



