AGRICULTURAL BOTANY. 221 



of the more recent theories of soil fertility and especially to the possible beue- 

 ficial effect of manganese salts in aiding the functioning of the oxidases. 



Compensation for the unexhausted manurial values of feeding stuffs and 

 fertilizers, J. A. Voelcker and A. D. Hall (Jour. Roy. Agr. Soc. England, 74 

 (1913), pp. 104-119; abs. in Mark Lane Express, 111 {1914), No. 4306, p. 539).~ 

 A revision of tables, last published in 1902 (E. S. R., 14, p. 1057), is reported 

 and discussed. The revision was rendered necessary by the recent rise in 

 prices of fertilizing materials, more particularly of those furnishing nitrogen, 

 and by the growing conviction that the spreading of compensation over a period 

 of four years is alilje inconvenient and not borne out by recent investigations 

 nor in actual agricultural practice. In the revision, therefore, the unit value 

 of nitrogen is taken as 15 s. ($3.65) instead of 12 s. ($2.92) as formerly, and 

 the compensation extends only to one crop after the fertilizing material is 

 applied. The prices for potash and phosphoric acid as used in the computation 

 of the table remain unchanged. 



AGRICULTTJRAL BOTANY. 



Studies in plant physiolog'y, P. Maze (Ann. Inst. Pasteur, 25 (1911), No. 10, 

 pp. 705-738, pi. 1, figs. 12; 27 (1913), Nos. 8, pp. 651-681, pi. 1; 12, pp. 109S- 

 1143, pis. 2, figs. 6; 28 (1914), No. 1, pp. 21-68, pis. 4, figs. 8).— This is a series 

 of memoirs in which the author attempts to establish the normal behavior of 

 the roots of the higher plants and the mineral nutrition of plants in relation to 

 a rational system for the use of fertilizers. IMost of his experiments were car- 

 ried on with maize, but various phases of the study were extended to other 

 plants to confirm the results obtained. Among the various topics discussed are 

 absorption and excretion of mineral substances by the roots and leaves of 

 plants, excretion of organic materials, relation of the constitution of nutrient 

 solutions to the mineral content of maize, storing mineral substances in different 

 parts of the plant, effect of incomplete solutions on the ash of maize, absorption 

 of organic matter and its use by the plant, the law of minimum in its physio- 

 logical relations, the role of water in plants, the mechanism of absorption, the 

 function of root secretions, conditions for fruiting of maize grown in aseptic 

 solutions, influence of various compounds on the development of maize, chlorosis 

 in maize, etc. Some of these topics have already been reported upon (E. S. R., 

 25. p. 224; 27, p. 721; 29. p. 82G). 



Notes on the technique of the determination of the depression of the 

 freezing point of vegetable saps, R. A. Goktnee and J. A. Harris (Plant 

 World, 17 (1914), No. 2, pp. 49-53). — A description is given of a method devised 

 by the authors for the rapid study of the depression of the freezing point of 

 vegetable saps. This method was successfully used in determining specific 

 gravity, total solids, freezing point depression, and electrical conductance of 

 more than SOO samples in about 2 months' time. 



Utilization of solar energy by green plants, A. PtJTTER (Natwrwissenschaf- 

 ten, 2 (1914), No. 8, pp. 169-175). — Results are given of experiments in which 

 the utilization rate of solar energy by various plants is said to have ranged 

 from 0.27 to 5.24 per cent of that incident on the green leaves employed. 



The influence of humidity and dryness on the anatomical structure of two 

 tropical plants, P. Choux (Rev. G6n. Bot., 25 (1913), No. 292, pp. 153-172, 

 figs. 16). — Giving results of a study regarding the external appearance, internal 

 structure, etc., as related to seasonal humidity in case of Ipomcea reptans and 

 Neptunia prostrata, the author states that the difllereuces are marked as regards 

 dimensions, color, and resistance. It is noted that in dry seasons the vascular 



