70 . Hydration and Growth. 



TABLE 58. 



p. ct. 



Swamp water 14 



Swamp water, citric acid, 0.01 N 15 



Potassium nitrate, 0.01 M 14 



Citric acid, 0.01 N '.'.'.'.'. 7 



Potassium nitrate, citric acid, 0.01 N 9 



Potassium hydroxid, 0.01 M 12 



The measurements in swamp water alone and with acid include the 

 full increase in 96 hours, while the others extended over from 20 to 

 40 hours. 



No important effect can be ascribed to the acidification of swamp 

 water. The swelling of the sections in the hundredth-molar solution 

 of potassium nitrate was but little below that in the swamp water, but 

 when this solution was similarly and equally acidified, a decrease 

 ensued. The foregoing tests were made with sections in a living con- 

 dition, in which questions of permeability and osmotic action might 

 possibly play a part. Material was prepared to exclude the action of 

 the living cell. The chlorophyllous layers were removed from the two 

 sides of joints of Opuntia and slices 7 mm. in thickness were cut in the 

 plane of the joint and placed between two sheets of filter-paper, to 

 one of which they adhered. A third sheet was laid over them and 

 the preparation placed on a wire netting to dry without pressure. In 

 6 days the thickness had been reduced to about 0.5 mm. and enough 

 moisture still remained to give the slices a leathery consistency. Suit- 

 able sections free from visible fibrovascular tissue were prepared which 



gave swellings as follows: 



TABLE 59. 



Living sections. Dried sections, 



p. ct. p. ct. 



Distilled water 660 47 



Bog water 640 45 



Swamp water 530 38 



Culture solution, 0.5 per cent 625 44 



The measurements were taken at the end of 24 hours, when a fair 

 rate of increase was still noticeable which would in the end have carried 

 the figures up to the next hundred in the dried sections. The swelling 

 of living material in bog water is but little less than in distilled water 

 and is also but little different from that in the culture solution, which 

 is of the concentration used in water cultures. Hydration is, however, 

 noticeably less in swamp water. 



Attention was now turned to the biocolloids to ascertain whether 

 the action of plant material living and dried would find a parallel in 

 the action of mixtures of known composition. Sections of plates 

 composed of agar (90) and oat protein (10) were found to show the 

 following swellings at 15C. 



TABLE 60. 



p. ct. 



Distilled water 2, 188 



Bog water 2,083 



Swamp water 1,200 



