

276 



BOTANICAL GAZETTE 



[OCTOBER 



under conditions favorable to the formation of a combination of 

 agar with ammonia or its closely related compounds. The exact 

 nature of these agar combinations and the manner in which water 

 acts upon them have not as yet been determined with any degree 



Swelling of dried 



o 



TABLE VIII 



"kaliated" and 



"ammonated" 



AGAR 



PLATES AT 15 C; ACTUAL SWELLING IN WATER OF " KALI- 



ATED 



yj 



PLATE 3450 PER 

 PER CENT 



"ammonated" plate 2450 



Plate 



Wt 



\\ ater 



0.01 N 

 KOH 



0.001 N 

 KOH 



0.01 N 

 NH 4 OH 



0.001 N 

 NH4OH 



"Kaliated" 



IOO 

 lOO 



57 



83 







"Ammonated" 



107 



122 









-^h ■* H ■ 



of satisfaction. Ammonium salts, such as ammonium chloride 

 and ammonium acetate, in the concentrations thus far tried, have 

 shown no augmenting effect on the swelling. Ammonium acetate, 

 although neutral in water solution, is hydrolyzed to a considerable 

 extent with the formation of the ions of ammonium and acetic acid. 

 The effect of these salts, in which the nitrogen can be considered as 

 fully satisfied, on the swelling of agar shows a typical neutral salt 

 effect. 



TABLE IX 



Swelling of dried plates of agar at i5°C. in solutions 

 of ammonium chloride and ammonium acetate; total 

 swelling of agar plates in water 1700 per cent 



Normal concentration 



Water 



NH 4 C1 



NR.COiCH, 



O.OI 



IOO 

 IOO 



58 

 94 



58 



IOO 



O.OOI * 





^» ^w ^*^ 



An examination of the records produced by swelling agar in 

 which the solutions are regularly renewed indicates clearly that 



ammonium 



to values in water =100; in 



N NH 4 OH 



distinctly the subsequent swelling of the already partially hydra ted 

 agar (figs. 3,4). Thus, for example, sections of agar had swelled 



= 25. After the 

 sections had attained their full swelling of 25 in 0.01N NH 4 OH, 

 the hydroxide solution was replaced by water. The agar swelled 

 further to a value equal to 73. Thereupon other sections of dried 









