192 PHYSIOLOGY [Bot. Absts., Vol. VI, 



injurious modification of the surface layer alters electrical potential. The author traces the 

 similarity with the "local-action" theory of corrosion (the chemical effect being due to local 

 electrical currents formed between adjoining areas of the metalic surface differing in compo- 

 sition or physical state) and considers in detail the characteristics of the propagation of 

 such oxidation on wires and the resemblances between this and protoplasmic transmission. 

 This similarity is not complete because of the structure of the protoplasm, the surface in 

 living matter being the surface of the protoplasmic films and lamellae and not solely that of 

 the cell.— H. E. Pulling. 



DIFFUSION, PERMEABILITY 



1309. Collip, J. B. Maintenance of osmotic pressure within the nucleus. Jour. Biol. 

 Chem. 42: 227-235. 1920. — It is suggested that the concentration of amino-acid and other 

 nitrogenous solutes of small molecular weight in the nucleus is sufficient to maintain its 

 osmotic tension. — G. B. Rigg. 



1310. Curtis, Otis F. The upward translocation of food in woody plants. II. Is there 

 normally an upward transfer of storage foods from the roots or trunk to the growing shoots? 

 Amer. Jour. Bot. 7: 286-295. 1920. — The common belief that food stored in the roots and lower 

 trunks of trees is carried upward in the spring and used in shoot formation is shown to rest 

 on evidence which is not conclusive. The author discusses and criticizes this evidence. In 

 his own work with ringed branches, he finds that when a ring is made on that part of a stem 

 which is from 5-15 or more years old or from 1-4 or more centimeters in diameter, the growth 

 above the ring approximates that of a normal stem. Evidently upward movement of foods 

 from points below the ring is not essential. In cases where growth has been somewhat less- 

 ened by ringing, this may be due to deficiency of water owing to the prevention of the forma- 

 tion of a new layer of xylem. When little stored food is available considerable shoot growth 

 may still take place owing to the production of food by the leaves of the young shoot itself. 

 Data are not sufficient to indicate how far back from the tip the food is withdrawn for use in 

 shoot growth. The author believes that normally there is no upward movement of foods 

 from the roots and perhaps little or none from the main trunk. He suggests that food stored 

 in roots is used solely in root growth. — E. W. Sinnott. 



1311. Loeb, Jacques. On the cause of the influence of ions on the rate of diffusion of water 

 through collodion membranes. I. and II. Jour. Gen. Physiol. 2: 387-408, 563-576. 1920 — 

 The similarity between the effects of electrolytes on free osmosis and electrical endosmose 

 is demonstrated, and, since the effects of electrolytes on electrical endosmose seem best to 

 be ascribed to their influence on the density of electrical charge on the membrane, it is con- 

 cluded that the effect of electrolytes on free osmosis through a collodion membrane can be 

 explained on the same basis. On the basis of the Helmholtz theorj r of electrical double lay- 

 ers, it seems that the ion having the same sign of charge as the membrane increases the dif- 

 fusion of water towards the solution side of the membrane, while that ion having a charge 

 opposite to that of the membrane decreases the charge on the latter and decreases the dif- 

 fusion of water. The effects on the ions vary at different concentrations. — O. F. Curtis. 



1312. Paxtaxelli, E. Alterazioni del ricambio e della permeabilita cellulare a tempera- 

 ture prossime al congelamento. [Changes in cell permeability at temperatures very near freez- 

 ing.] Atti R. Accad. Lincei Rend. (CI. Sci. Fis. Mat. e Nat.) 28 l : 205-209. 1919.— It was 

 found that the cells of the endocarp of the mandarin orange {Citrus nobilis) when subjected 

 to temperatures very near to freezing suffer a progressive increase in the cell permeability. 

 This is made evident by a rapid emission of water from the tissue when it is kept dry, or by 

 an exosmosis of substances from tissue immersed in water. This is favored by such sub- 

 stances as penetrate rapidly into the cells (glycerin, ethyl alcohol, citric acid, and free alkali) ; 

 there is also a rapid destruction of sugar, limited by the supply of substances that may be 

 absorbed and utilized for respiration (glycerin, ethyl alcohol, citric acid) or by such substances 

 as curb the exosmosis of the sugars or by the intermediate products of respiration (sodium 



