AGEICULTUEAL BOTANY. 29 



The American fertilizer handbook {Philadelphia: Ware Bros. Co., 1915, 8. 

 ed., pp. 402, figs. 19). — This handbook contains, as usual, directories of fertilizer 

 manufacturers, allied fertilizer trades, cotton-seed oil mills, chemists and engi- 

 neers, fertilizer materials- and machinery, and packers and renderers, together 

 with special articles, statistics, and miscellaneous information relating to the 

 fertilizer industry. Among the more important special articles included are the 

 following : 



German and other Sources of Potash Supply, by C. H. MacDowell ; The 

 Sulphuric Acid Industry, by A. M. Fairlie; Dictionary of Fertilizer Materials, 

 by T. C. Pinkerton ; Five Years of Cyanamid in America, by E. J. Pranke ; 

 Phosphate Rock Production in 1913, by W. C. Phalen ; Phosphate Rock Pro- 

 duction in 1914, by W. C. Phalen; Florida Phosphate Rock, 1914, by E. H. 

 Sellards ; The Products and Composition of Cotton Seed, by T. C. Low ; Cotton- 

 seed Meal as a Fertilizing Material, by A. M. Soule ; and The Western Animal 

 Ammoniate Market, by J. B. Sardy. 



AGRICULTURAL BOTANY. 



Studies on periodicity in plant growth. — I, A four-day periodicity and root 

 periodicity, R. A. Robertson and Rosalind Crosse (Proc. Roy. Soc. Edinh., 

 83 {1912-13), No. 1, pp. 85-102, pis. 3, figs. 2).— This study as described has led 

 to the general conclusions that there occurs in elongating plant organs a four- 

 day periodicity apparently due in part to internal causes, but also aifected by 

 external conditions. Roots exhibit a daily periodicity, which is correlated with 

 that shown by the stem. 



Studies on periodicity in plant growth. — II, Correlation in root and shoot 

 growth, Rosalind Ckosse {Proc. Roy. Soc. Edinh., 35 {1914-15), No. 1, pp. 

 46-53, pis. 2) . — The author reports an extension of the work above noted. 



It is stated that the root and shoot rhythms are correlated, varying with 

 changing conditions. No evidence has been obtained regarding the disap- 

 pearance of the periodicity under uniform conditions, whether of light or dark- 

 ness, indicating the automatic nature of the phenomenon. 



An automatic method for the investigation of velocity of transmission of 

 excitation in Mimosa, J. C. Bose {Phil. Trans. Roy. Soc. London, Ser. B, 204 

 (1913), No. 305, pp. 63-97, figs. 25). — Giving an account of studies on Mimosa 

 by means of apparatus for which great delicacy is claimed, the author holds 

 that the results obtained prove that the transmission of excitation is a process 

 fundamentally alike in animals and in plants, being in both cases a propagation 

 of protoplasmic change. 



The influence of homodromous and heterodromous electric currents on 

 transmission of excitation in plant and animal, J. C. Bose {Proc. Roy. Soc. 

 [London], Ser. B, 88 {1915), No. B 607, pp. 483-507, figs. 10).— The author gives 

 an account of studies, suggested by the results of the studies above noted, on 

 the variations of conductivity produced by the directive action of an electric 

 current. 



It is stated that in the conducting tissue of a plant, as in the nerve of an 

 animal, the passage of a current induces a variation in the conductivity as 

 regards excitation. In cases involving feeble intensity, a heterodromous cur- 

 rent, or one opposite in direction to that of propagation of excitation, enhances 

 the conduction of excitation, while a homodromous current or one in the direction 

 of propagation of excitation, depresses it. The after effect of a current is a 

 transient conductivity variation, opposite in sign to that induced during the 

 continuation of the current. The normal conductivity variation undergoes a 

 reversal under a strength of current above the critical value, the heterodromous 



