VI. REACTIONS OF BIOCOLLOIDS AND CELL-MASSES TO 



CULTURE SOLUTIONS, BOG. SWAMP, AND GROUND 



WATER. AND OTHER SOLUTIONS. 



The organism encounters a variety of substances in solution in the 

 substratum or medium to which, of course, the colloids of the cell re- 

 act in a manner determined by their own composition and that of the 

 impinging substances. The securest knowledge of the complex rela- 

 tions involved will in the end rest upon results obtained by analytical 

 experiments in which the effects of separate substances and graded 

 concentrations of the elements are first determined and then their 

 action in combination is measured. Meanwhile, a number of standard 

 or commonly accepted solutions are used for a variety of cultural and 

 experimental purposes and an effort was made to ascertain the reactions 

 of biocoUoids and of sections of plants to them in terms of imbibitional 

 swelling. The idea was extended to include the "natural waters" 

 which are characteristic of some well-defined plant habitats, such as 

 bogs and swamps. 



A large and important share of the knowledge of the physiology of 

 plants rests upon cultures made with " nutrient solutions." One of 

 these, after a formula devised by W. E. Tottingham, was chosen for 

 the test.^ Its composition was: potassium nitrate 4.048 g., dipotassic 

 phosphate. 12.980 g., magnesium sulphate crystals 29.280 g., and cal- 

 cium nitrate 27.920 g., in 4,000 c.c. of water. A precipitate comes 

 down in the bottle on standing. This was filtered out and dissolved 

 in distilled water, which was used to dilute the solution to a concen- 

 tration of about 0.5 per cent total concentration. 



The preliminary trial of the effect of the whole solution was made 

 with sections of a plate consisting of 95 parts agar and 5 parts of bean 

 protein, an old preparation which had been exposed to the damp air 

 for a month. The swelling measurements were as follows : 



Table 52. 



p. ct. 



Water 617.6 



Nutrient solution, 0.5 p. ot 500 



Citric acid, 0.01 N 406.8 



Sodium hydroxid, 0.01 M 431 .4 



The only feature of interest in the results was the low imbibition in 

 water, the dried sheet being an old one. A fresh preparation was 

 made with the agar and bean protein in the same proportion as before, 

 and a double series of instruments was used in the test. 



In order to determine the possible interference or antagonism of the 

 constituents, tests were also made of the separate action of the four 



1 Tottingham, W. E. A quantitative chemical and physiological study of nutrient solutions for 

 plant cultures. Physiol. Res., 1: No. 4. May 1914. 



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