Effect of Certain Organic Adds and Amino Compounds. 63 



and from the swelling of plants makes it fa;irly certain that the effect 

 is due primarily to the action of the pentosans. 



The most recent tests of the effects of glycocoU on plants are those 

 of Borowikow/ completed in 1913 arid pubUshed in the same year, and 

 those of Dachnowski, brought out in 1914.^ Borowikow took the 

 position that substances which facilitate hydration of the plasmatic 

 colloids accelerate growth, and that such hydration was one of pro- 

 teins, an assumption which is not sound. His trials consisted in com- 

 paring the growth of seedUngs of Helianthus in distilled water as a 

 check or control with the substances to be tested added to water, the 

 measurements being taken during a few hours only. GlycocoU was 

 used in 0.01 N and 0.005 N concentration. Such concentrations are 

 relatively high for the plant, and only retardation effects were obtained. 



Dachnowski's figures indicate that glycocoU added to hydrochloric 

 acid in concentrations of N/1,600 (50 c.c. N/800 of each substance) 

 causes an increase in the amount of water absorbed by bean seeds, 

 and a lesser increase of hydration in corn seeds. 



Both absorption and transpiration by cuttings of tomato were less 

 in solutions of hydrochloric acid ranging from N/800 to N/6,400 than 

 in water, but this retarding effect was counteracted to some extent 

 when glycocoU was added to the solutions. This amino-acid also 

 caused an increased gain in weight in acid and alkaline solutions. 



The hydration phenomena described in the preceding pages afford 

 some interesting paralleUsms with the action of these compounds on 

 growth, absorption, and transpiration. 



It is evident that we must definitely and finally cease to treat a plant 

 cell-mass as an amphoteric colloid with a dissociation expressed by the 

 actual acidity of the ceU-sap. Such dissociation and resultant hy- 

 dration capacity may determine the action of protoplasts or of cell- 

 organs which are chiefly proteinaCeous. 



Vegetative cell-masses such as are responsible for growth, and the 

 activity of which constitutes growth in the larger sense, are composed 

 of colloids predominantly of a carbohydrate character. These pen- 

 tosans do not dissociate. Their swelling capacity in electrolytes is 

 less than in pure water. The hydration of agar and the pentosans in 

 acids is retarded or lessened by the action of H ions, so directly that 

 the proportionate swelling of agar in an acid such as acetic or succinic 

 might be used as a measure of the concentration of the acid solution 

 (see p. 57). This fact and the part played by the dissociation of 

 gelatine may be traced through all of the results on hydration of agar, 

 agar-gelatine, and agar-protein mixtures. Thus, for example, agar 



' Borowikow, G. A. Ueber die Ursachen des Wachstuma der Pflanzen. Biochem. Zeitsohrift, 

 50: 119. 1913. 



^ Dachnowski, A. The effects of acid and alkaline solutions upon the water-relations and the 

 metabolism of plants. Amer. Jour, of Bot., 1: 412-439. 1914; also, Dachnowski and Gormley. 

 The physiological water requirement and the growth of plants in glycocoU solutions. Amer. 

 Jour, of Bot., 1 : 174-185. 1914. 



