72 Hydration and Growth. 



The imbibition capacity of the biocolloids varies with the propor- 

 tions between the* carbohydrate and the proteins and protein deriva- 

 tives. A biocolloid was subsequently made up which included a high 

 nitrogen-content and a second carbohydrate and five albuminous com- 

 pounds. For this purpose, 70 parts agar, 5 parts each of dextrose, 

 peptone, gelatine, asparagin, nucleinic acid, and bean protein were 

 suitably liquefied and poured into plates which dried down to a 

 thickness of 0.2 mm. Swellings of sections of these plates at 15 C. 

 gave the following increases at the end of 24 hours : 



TABLE 63. p. ct. 



Distilled water 725 



Bog water 592 



Swamp water 550 



Calcium chloride, 0.2 M 350 



Calcium chloride, 0.1 M 400 



The total swelling in distilled water for this biocolloid is low, al- 

 though it is to be noted that swellings as high as 1,200 per cent in dis- 

 tilled water have been measured at temperatures of 18 to 20 C. 



Sections from plates made up as above, but to which had been 

 added 0.8 per cent of culture salts, gave increases as follows at tem- 

 peratures of 15 C. : 



TABLE 64. p. ct. 



Distilled water 600 



Bog water 525 



Swamp water 625 



This complex biocolloid, high in nitrogen and in the culture salts, 

 displays hydration capacity in swamp water superior to that shown in 

 bog water or pure water. The properties in question would enable a 

 plant so equipped to thrive in the waters of swamps, and it would be 

 interesting to determine whether such a condition actually prevails 

 in the plants of the sedgy swamps. 1 



The earlier attempts to interpret the swelling action of protoplasm 

 were founded on the assumption that such increase might be repre- 

 sented by the action of gelatine. The unsoundness of this assumption 

 and the inadequacy of the methods using this material have been 

 amply demonstrated by results previously published. At one end of 

 the scale stand some plants and some plant structures high in protein- 

 aceous compounds and low in pentosans, and these do show a behavior 

 approximating that of gelatine. This is illustrated by the following 

 series, in which sections of gelatine plates 0.18 mm. in thickness were 

 swelled at 15 C., giving measurements as follows: 



TABLE 65. p. ct. 



Distilled water 778 



Bog water 889 



Swamp water 939 



Culture solution, 0.5 per cent 889 



Potassium nitrate, 0.01 M 911 



1 Schimper, A. F. W. Die Indo-Malayscher Strandflora, p. 142. 1891. 



