152 MacDOUGAL and SPOEHR— COMPONENTS AND 



tions given. Their hydration is but Httle affected by the presence 

 of the common sugars in the water of suspension or dispersion. 



X. The albumins and their derivatives are amphoteric, being 

 capable of dissociating both as acids or as bases. Hydration in the 

 presence of hydrogen ions may be much greater than in water and 

 may reach the possible maximum, while that in the presence of 

 hydroxyl ions and of various cations may also be in excess of that 

 in water. Gelatine as an example of this group shows such behavior 

 but has a restricted hydration capacity in amino-acids such as gly- 

 cocoll. On the other hand, the swelling is proportional to the high 

 hydrogen ion concentration of such amino-acids as aspartic acid, 

 which is diabasic. 



XI. Variations in the hydration total or volume may be ascribed 

 to changes in the colloidal components of a plasma, to products of 

 the resident metabolism, to the action of substances absorbed during 

 hydration or to fluctuations in temperature. 



XII. The changes in volume of a mass of colloidal material are 

 usually not iso-diametrical during hydration. Such alterations are 

 determined by the structure of the jelly which may be so dift'er- 

 entiated as to show expansion and contraction along one axis almost 

 wholly. 



XIII. The analysis of the implied facts has also demonstrated 

 that growth is so essentially as to its nature, and so largely as to 

 volume, a matter of hydration that the compounds which facilitate 

 the sweUing of phytocolloids and of cell-masses, facilitate or accel- 

 erate growth.^ 



1 MacDougal, D. T., " Hydration and Growth," Publ. 297 Carnegie Inst, 

 of Wash., 1920, and " Hydration Effects of Amino-compounds," Proc. Soc. 

 for Exper. Biol and Med., 17: 35-36. 1919. 



Schreiner, O., and Skinner, J. J., " Experimental Study of the Effect of 

 Some Nitrogenous Soil Constituents on Growth. Nucleic Acid and Its De- 

 composition Products," Plant World, 16: 45-60. 1913. 



Schreiner, O., and Skinner, J. J., " Specific Action of Organic Compounds 

 in Modifying Plant Characteristics; Methyl GlycocoU versus Glycocoll," Bot. 



Gac, 59: 445-463- 1915- 



Skinner, J. J., and Beattie, J. H., " Effect of Asparagin on Absorption and 

 Growth in Wheat," Bull. Torr. Bot. Club, 2,9: 429-437- IQIP-, 



Borovicow, G. A., " On the Action of Different Substances on the Veloc- 

 ity of Growth of Vegetables," Publ. of the Soc. Nat. of New Russia, 41 : 

 15-194. 1916. 



