June 27, 1919] 



SCIENCE 



603 



was found to show a swelling in hundredth 

 normal acetic acid fifty per cent, greater than 

 in distilled water, agar forty per cent, less, and 

 a combination of eight parts of agar and two 

 parts of albumin, about forty per cent, less 

 than in water. 



The hydrogen ion concentration of the 

 fluids in a plant cell are controlled by the 

 buffer conditions which exist there, but still 

 the range of variation, is much wider than that 

 found in the circulatory systems of animals. 

 Bases or cations are seen to affect the swelling 

 of the plasmatic mixtures in my experiments. 

 Various authors having secured results indi- 

 cative of accelerating effects of certain amino- 

 conipounds on growth, some swelling tests of 

 the effects of these substances were made with 

 the discovery that such an amino-acid as glyco- 

 coll in hundredth molar solutions seems to 

 retard the swelling of gelatine, at least when 

 the increase in thin dried plates is considered, 

 and to accelerate the swelling of agar to and 

 beyond the total in water. The mixture of 

 agar and albumin, as well as a mixture of 

 agar and gelatine, shows a greater hydration 

 in glyeoeoll than in water. 



The possible physiological significance of 

 these results is heightened by the knowledge 

 of the fact that some of these amino-com- 

 pounds may be taken to be universally present 

 in growing cells and they probably vary less 

 than the organic acids. It is suggested that 

 the ammonia group in these compounds may 

 form a salt with the carbohydrates with the 

 effect of increasing the hydration capacity. 

 ^Vllether any reaction with, or effect upon, the 

 hydration of the protein element occurs is not 

 yet clear, although it is obvious that such ac- 

 tion might be of fundamental importance in 

 nutritive metabolism. The entire matter of 

 hydration may be briefly summarized by the 

 statement that the fundamental properties of 

 a colloidal mixture or of living matter will de- 

 pend ujwn the proportion of albumins and of 

 pentosans, and upon the properties of the par- 

 ticular substances of each group which may be 

 present. Hydrogen ions within the possible 

 range of concentration increases hydration of 

 the albuminous substances and depress that of 



the pentosans. Bases or cations exert a re- 

 verse effect on the albuminous substances and 

 depress hydration of the pentosans slightly. 

 Certain amino-compounds depress the swell- 

 ing of albuminous compounds, but facilitate 

 the hydration of pentosans and sections of such 

 substances when mixed in a proportion of four 

 to one with albumin undergo hydration to a 

 degree equivalent to or even greater than that 

 in water. 



The second phase of growth, that of the in- 

 corporation of molecules of solid matter is not 

 so easily described since it is not so directly 

 susceptible of experimental test. If the con- 

 ception of the pentosan-albumin composition 

 of protoplasm is correct, it is obvious that the 

 mass of living matter may not be increased 

 simply by the addition or diffusion of sugars 

 into the meshwork, as is supposed by some 

 writers. 



Before the material in these carbohydrates 

 may actually become a part of the colloidal 

 living mesh it is undoubtedly broken down to 

 some extent by enzymatic or respiratory ac- 

 tion, part of the material being carried through 

 transformations to organic acids or carbon 

 dioxide, some of the material is combined 

 with the ammonia group (NH.^) to form 

 amino-compounds, some with the lipins, while 

 some of these sugars may be converted to the 

 pentose form in which they would so mark- 

 edly affect the hydration capacity of the mass. 



By way of crude illustration, protoplasm 

 might be regarded as the wick of a lamp 

 which draws sugar into its meshes, burns the 

 sugar and in the burning some of the sugar not 

 completely consumed unites with other sub- 

 stances to form additional fibers of the wick. 



At this point it would be well to divert at- 

 tention for the moment to the so-called " nu- 

 trient " salts, the presence of which in the soil 

 and in the liquids of the plant is so indispen- 

 sable to the plant. It is necessary for an 

 understanding of the real nature of growth to 

 have clearly in mind that living matter is a 

 colloidal mixture of proteins and carbohy- 

 drates, which takes up water and gains solid 

 material in growth by processes which are 

 actually retarded by these salts. These com- 



