AGRICULTUKAL BOTANY. 625 



embryo, increasing and decreasing the oxygen concentration, and direct meas- 

 urement of tlie oxygen intake with intact and seared seeds, and witli seeds in 

 varying concentrations of oxygen. It is thouglit that after-ripening may 

 consist in an increased permeability of the seed coat to oxygen, together with 

 a rise in the embryo acid content, which is accompanied by an increased water 

 iibsorbing power of the embryo. 



A bibliography is appended. 



Transpiration in relation to growth and to the successional and geo- 

 graphic distribution of plants, A. Dachnowski (Ohio Nat., J-J (1914), No. 4, 

 pp. 241-251). — Discussing the results of work previously reported (E. S. II., 28, 

 p. 733), the author considers it probable that the absorbing ix>wer of the root 

 system of a plant is not regulated by the amount of water transpired but by 

 the differential permeability of the absorbing epidermal root cells and the 

 metabolic requirements during the life cycle; that absorption of inorganic 

 and organic constituents is not connected with transpiration but with meta- 

 bolism; and that no direct relation exists between growth, green and dry weight 

 of plants, and trausijiration, even under the same conditions of experiment. 

 The rate and amount of gi-owth and final size of a plant depend in part on 

 favorable conditions of temperature, light intensity, food supply, and amount 

 of water present in the plant, the rate or total amount of water transpired 

 giving no indication as to the quantity normally required for metabolic processes 

 and for gi-owth. It is held that the quantity of transpiration water in most 

 plants is not coordinated with or directly related to the absorption and trans- 

 location of solutes or to the gx'een and dry weight of plants, that it is not an 

 index of metabolism and growth or vegetable luxuriance, but that it has its 

 own advantages, such as protection from high temperatures in direct sunlight 

 and aid iu gaseous exchanges. It is thought that transpiration may be a factor 

 in determining the final form of plants. 



The physiological water requirement and the growth of plants in glyco- 

 coll solutions, A. Dachnowski and R. Gormley (Anier. Jour. Bot., 1 {1914), 

 No. 4, pp. 174-185; a&s. in SHence, n. ser., 39 (1914), No. 1017, p. 056).— This 

 paiier, though regarded as of a preliminary nature, continues iihysiological 

 studies of Dachnowski (see above). 



Tabulated results are given of experiments with bog plants tested in regard 

 to transpiration and growth in glycocoll solutions of varying strength. It is 

 stated that the transpirational water loss In the experiments cited is a func- 

 tion of the vapor pressure of the water, affected by the quantity of salts in 

 solution and the factors modifying the atmospheric conditions. The absorption 

 of glycocoll is not connected with the transpirational water loss, but with the 

 differential permeability of the absorbing root cells, with the efficiency of the 

 nutritive metabolism characteristic of the plants, and with the amount of water 

 retained within the plants. 



The insufficiency of a salt operates as a limiting factor to growth, but 

 transpiration does not decrease consistently with retardation thereof. The 

 amount of water retained is decreased when the strength of the solution passes 

 a certain optimum concentration, the available water rather than the solut'3 

 becoming then the limiting factor, unlike plants reacting differently to physio- 

 logically limiting water conditions. The variations appear to be inherent 

 peculiarities of the growth capacity and metabolism of plants. Plants may 

 show loss in weight without a corresponding loss in amount of water transpired, 

 or an increase of growth may occur with little or no increase in transpiration. 

 A decrease in the increment of body weight may arise through faulty nutri- 

 tion and enforce compensating processes. Weaker acid solutions are more 

 effective than stronger solutions in affecting the hydration capacity of tissue*?, 



