66 PHYSIOLOGY [Bot. Absts., Vol. VII, 



The growth rate for the entire season conforms to that of a chemical reaction consisting of 

 two unimolecular reactions, one of which alternately accelerates and retards the other, 



X = 210 [1 - e- 095(1-1)] +19.1 L-.osst cos ^ t1 



If growth be assumed to be proportional to the amount of active catalyst present, a method is 

 available for studying the dynamics of the growth process. — H. S. Reed. 



MOVEMENTS OF GROWTH AND TURGOR CHANGES 



431. Jaccard, p. Inversion de I'excentricite des branches produite experimentalement. 

 [The experimental inversion of the eccentricity of branches.] Rev. Gen. Bot. 32:273-281. 

 2 jpl., 1 fig. 1920. — Many authors have considered the eccentric growth of the lateral branches 

 of trees to be the result of the polarizing action of a geotropic excitation having its seat in the 

 terminal portion, and have therefore called the wood of the larger side "geotropic wood." 

 If growing branches are tied in the form of a circle with the upper face on the inside, thus 

 reversing the usual tension-compression relation of the upper and lower faces, a reversal of 

 the eccentricity occurs. The eccentricity is therefore due to the mechanical action of weight 

 (tension and compression) on the growing tissues, and not to a geotropic excitation. This 

 conclusion is supported by the behavior of plants kept for some months on a large clinostat. 

 Here also the eccentricity is reversed; because of a slight centrifugal force (1/20 gravity) 

 developed by the clinostat, the upper face of the branch is more strongly compressed during 

 one half of the rotation than is the lower face during the other half. The same stimulus, 

 such as longitudinal compression, accelerates wood formation in some species and retards it in 

 others. Conifers and dicotyledons differ in this respect. The increase in the thickness of 

 the wood on one side compensates for a decrease on the other; eccentricity involves no abso- 

 lute increase in the mass of woody tissue in a given length of the branch. — L. W. Sharp. 



GERMINATION, RENEWAL OF ACTIVITY 



432. Anonymous. Notes and comments. Australian Nat. 4: 160. 1920. — A seed ger- 

 minating in one year instead of the usual two. — T. C. Frye. 



433. Lesage, p. Contributions a I'etude de la germination des spores de mousses. 

 [Germination of moss spores.] Compt. Rend. Acad. Sci. Paris 166: 744-747. 1918. — The 

 author shows that the spores of certain mosses are capable of germination after being dried 

 for periods of from 3 to 7 years. In the case of Funaria hygrometrica, which proved an espe- 

 cially good species for experimental purposes, he found that the optimum temperature for 

 germination was between 21 and 22°C.; that darkness retarded the germination; and that 

 spores sown in distilled water germinated better if the vessels of distillation were glass rather 

 than copper. — A. W. Evans. 



TEMPERATURE RELATIONS 



434. CoviLLE, Frederick V. The influence of cold in stimulating the growth of plants. 

 Proc. Nation. Acad. Sci. [U. S. A.] 6: 434-435. 1920. — The attainment of winter dormancy by 

 trees and shrubs is not dependent upon exposure to cold. Experiments with controlled 

 temperatures further indicate that a period of chilling is necessary for normal resumption of 

 growth in the spring; in plants kept warm throughout the winter, the spring growth is delayed 

 and abnormal. Exposure to cold results in transformation of stored starch to sugar, with 

 the consequent development of high osmotic pressures. — Howard B. Frost. 



435. Matisse, G. Action de la chaleur et du froid sur I'activite des etres vivants. [Action 

 of heat and cold upon the activity of living organisms.] u + 556 p., 175 fig. Emile Larose; 

 Paris, 1919. — According to the author he has attempted in this work to correlate the viewpoint 



