354 THE JOURNAL OF INDIAN BOTANY. 



Small, James " The Chemical Reversal of Geotropic Response in 

 Roots and Stems" — The following abstract of a paver read before the 

 Linnean Society, March IS, 1920, is taken from the minutes of the 

 meeting. 



When roots are placed horizontally in a moist atmosphere rendered very 

 faintly alkaline by ammonia vapour they tend to grow upwards. When stems 

 are treated in a similar way with acetic acid vapour they tend to grow down- 

 wards. 



These experiments, illustrated by photographic lantern-slides, form preli- 

 minary confirmation of the following theory of geotropic curvature, which 

 has been elaborated as a co-relation of previous work on the electrical con- 

 ductivity of roots with data accumulated by other investigators. 



The outer zone of the protoplasm in the cells of the apical meristem is an 

 emulsion with a continuous phase of colloidal aqueous solution and a disperse 

 phase of protein or protein-lipoid particles, which show Brownian movement 

 and carry an electropositive charge when the hydrion concentration of the 

 continuous phase is higher than the isoelectric point of the vegetable proteins, 

 or an electornegative charge when that hydrion concentenation is lower than 

 the isoelectric point of the proteins. The continuous phase or medium in the 

 root is relatively acid and that in the stem is relatively alkaline. 



Creaming of the emulsion under the influence of gravity causes differen- 

 ces of potential in the apex of root and stem, which produce electric currents. 

 These produce differences in permeability, turgor, and rate of growth. The 

 direction of these currents is determined by the positive charge in the root 

 and the negative charge in the stem with corresponding downward or upward 

 curvature. 



The reversal of curvature in the experiments is due to the reversal of the 

 electrical charges on the particles of the disperse phase, which is caused by 

 the changes in the relation of the hydrion concentrations to the isoelectric 

 point of the proteins. This theory explains practically all the details of 

 known geotropic phenomena, including the orientation of the secondary and 

 tertiary branches of roots and stems. It has very wide applications to cyto- 

 lysis, the stimulus response ratio of the Weber Law, acid-tolerant and calci- 

 fuge species, immunity from and liability to attack by bacteria and fungi, the 

 development of intumescences, the effects of acids, alkalies, and salts on 

 plants and animals in general and on the permeability of protoplasm in parti- 

 cular, and possibly also to epharmonic variations. It provides on explana- 

 tion, not only for the normal polarity of growth in the plant, but also for 

 the changes in geotropic response and in colour which occur in flower-buds 

 and other organs. 



Indications have been obtained that the Co 2 balance in stem and root is 

 the chief factor governing the differentiation in hydrion concentration, and 

 also that phyllotaxis can be explained in terms of the potential differences 

 postulated. 



Heredity 



White, Orland E. Breeding new castor beans. Jour. Heredity 

 195—200- 5 figs. 1918. 

 The author calls attention to the desirability of developing improved 



