314 PHYSIOLOGY [BoT. Absts., Vol. VIII, 



2145. WiGGANS, R. G. Variation in the osmotic concentration of the guard cells during 

 the opening and closing of stomata. Amer. Jour. Bot. 8: 30-40. 'J fig. 1921. — Determinations 

 of the osmotic concentration of the guard cells and epidermal cells of Zebrina pendula, Iresine, 

 Cyclamen, and the beet were made by placing pieces of the epidermis in calcium chloride so- 

 lution of different densities and noting the concentration at which plasmolysis took place. 

 There was little change in the osmotic concentration of the epidermal cells during the day. 

 The concentration of the guard cells increased in the early hours of sunshine and decreased in 

 the afternoon, approaching the concentration of the epidermal cells at nightfall. It was 

 always higher in the guard cells than in the epidermis, though the differences were not as 

 great as those reported by Iljin. Concentrations were in all cases higher in experiments 

 carried on at Columbia, Missouri, than at Ithaca, New York. — E. W. Sinnott. 



WATER RELATIONS 



2146. Johnston, E. S. A method of studying the absorption-transpiration ratio in nutrient 

 media. Science 52 : 517. 1920. — Several writers have shown that the water content of plants 

 varies with the hour of the day. Wilting takes place when the ratio of the rate of entrance 

 to the rate of exit is less than unity, whether caused by excessive transpiration or by a decrease 

 in root absorption. These 2 processes may be studied by using water culture plants exposed to 

 different environmental conditions or placed in solutions of different osmotic pressures. An 

 experiment is described to illustrate the manner in which changes in the strength of solutions 

 affect the ratio of absorption to transpiration. — A. H. Chivers. 



MINERAL NUTRIENTS 



2147. HoAGLAND, D. R. Optimum nutrient solutions for plants. Science 52: 562-564. 

 1920. — The author raises the following questions: (1) Is it probable that the plant has any 

 definite response, within broad limits, to a particular ratio of salts or ions contained in the 

 complete nutrient solution? (2) Assuming the existence of such optimum solutions, are the 

 methods generally employed adequate to determine their composition? It has been shown 

 previously that often the total supply of nutrients may have limited the yield, and also the 

 insolubility of iron, when added in the form of phosphate. In connection with the first point 

 the following experiment may be suggestive: Three nutrient solutions were used with barley; 

 (a) solution used by the author, (b) Shive's best solution, (c) Shive's best solution diluted 

 to \ of the concentration in (b). Solutions (a) and (b) gave equally favorable growth, while 

 the smaller yield from (c) is not necessarily significant. In this experiment solutions of 

 radically different concentrations and salt proportions have not affected yield of crop to any 

 important extent. Certain solutions may, of course, inhibit plant growth because of un- 

 favorable physiological balance. Nevertheless, the range of equally favorable ratios between 

 nutrient salts is probably a very broad one, no doubt including the solutions of most soils. — 

 A, H. Chivers. 



2148. Jones, Henry Wallace. The distribution of iron in plant and animal tissues. 

 Biochem. Jour. 14: 654-659. 1920.— Making use in the main of Macallum's haematoxylin 

 method, the writer finds that inorganic iron is quite widely distributed throughout animal 

 and vegetable tissue, the lower organisms giving the reaction much more strongly than the 

 higher. Aquatic animals contain more such iron than terrestrial, and foetal tissues more 

 than adult. All nuclei show the reaction. — A. R. Davis. 



2149. McCall, a. G., and J. R. Hoag. The hydrogen-ion concentration of certain three- 

 salt nutrient solutions for plants. Soil Sci. 10: 481^85. Fig. 1. 1920.— Using Gillespie's 

 method of hydrogen-ion determination it was found that in general with any one type of 3- 

 salt nutrient solution the hydrogen-ion concentration is a function of the proportion of 

 KH2PO4 present. Types of solutions containing KH2 PO4 have a lower hydrogen-ion concen- 

 tration than^those containing Mg(H2P04)2 or Ca(H2P04)2. The sulphates and nitrates play 



