No. 1, February, 1921] PHYSIOLOGY 65 



424. LoTKA, Alfred J. Analytical note on certain rhythmical relations in organic systems. 

 Proc. Nation. Acad. Sci. [U. S. A.] 6: 410-415. 1920. — A discussion of mathematical laws of 

 some types of periodic phenomena. Certain applications of the laws of chemical dynamics 

 indicate the occurrence of damped (transitory) oscillations, and only such were expected "in 

 the absence of geometrical, structural causes." The author finds, however, that in certain 

 cases his method indicates undamped oscillations. Consider a system in evolution, where 

 species of matter (organic or inorganic) having the masses Xi, X2 . . . Xn are character- 

 ized by certain parameters Q and physically conditioned by other parameters P. "For a 

 very broad class of cases, . . . the course of events in such a system will be represented 

 by a system of differential equations of the form 



-^ = FiniXr, X, • • • 



The author here considers especially a simple case, that of the quantitative relations between 

 a plant species and an animal species feeding upon it. Undamped oscillations in the abun- 

 dance of the species are shown to result. — Howard B. Frost. 



425. MoREAU, F. (M. and Mme.) Recherches sur les lichens de la famiUe des Pelti- 

 geracees. [Researches on lichens of the family Peltigeraceae.] Ann. Sci. Nat. Bof. X. 1: 29- 

 138. IS pi, 23 fig. 1919.— See Bot. Absts. 7, Entry 371. 



426. PiETSCH, Albert. Wie erklart sich daslange Hangenbleiben der Blatter an einigen 

 phanerogamen Holzgewachsen im Herbste 1919? [What is the explanation for the late reten- 

 tion of the foliage of several phanerogamous woody plants in the fall of 1919?] Naturwiss. 

 Zeitschr. Forst-u. Landw. 18: 150-155. 1920.— See Bot. Absts. 7, Entry 140. 



GROWTH, DEVELOPMENT, REPRODUCTION 



427. Bernbeck. Das Wachstum im Winde. [Growth and wind.] Forstwiss. Centralbl. 

 42: 27-40, 59-69, 93-100. 1920.— See Bot. Absts. 7, Entry 113. 



428. Burns, George P. Eccentric growth and the formation of redwood in the main stem 

 of conifers. Vermont Agric. Exp. Sta. Bull. 219. 10 pp., 4 pi, 10 fig. 1920.— See Bot. 

 Absts. 7, Entry 318. 



429. Harvey, E. N. An experiment on regulation in plants. Amer. Nat. 54:362-367. 

 1 fi^. 1920. — An analysis of factors retarding lateral outgrowths of plants. The author recalls 

 the already known facts that growing stem tip or apical bud has inhibitory influences on 

 lower latent buds and that active root inhibits growth of others above it. He reports an 

 experiment to support the idea that regulatory influence of one part over another in plants is 

 not due to transport of materials. The author thinks that it is dependent on living proto- 

 plasts in the organism whose selective permeability leads to an electrical polarity that deter- 

 mines the biological polarity of the organism. — J. P. Kelly. 



430. Reed, H, S. The dynamics of a fluctuating growth rate. Proc. Nation. Acad. Sci. 

 [U. S. A.] 6: 397-410. 5 fig. 1920.— This is a study of the growth rate of a selected lot of 

 shoots on young apricot trees, with reference not only to the type of growth, but also to the 

 intraseasonal periodicity of growth. The growth rate exhibited its greatest velocity in the 

 early part of the growing season and declined as the season advanced, exhibiting three intra- 

 seasonal cycles of growth. The growth during each cycle is expressed by the formula of 

 autocatylysis, 



log — ^— = K (t - ti) 



BOTANICAL ABBTBACTB, VOL. VII, NO. 1 



