Decbmbeb 10, 1920] 



SCIENCE 



563 



tion of the solution or solutions best suited 

 to the growth of the plant. It now seems to 

 be an opportune time to raise the following 

 questions: first, 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; and second, 

 assuming the existence of such optimum 

 solutions, are the methods generally employed 

 adequate to determine their composition? 



With regard to the second point, in a 

 previous communication the writer'- has at- 

 tempted to show that in many experiments 

 the total supply of nutrients may have limited 

 the yield of crop, rather than the salt pro- 

 portion. In another article^ it is shown that 

 insufficient attention has been given to the 

 possible limitation on growth with certain 

 solutions, due to the insolubility of iron, when 

 this element is added in the form of the 

 phosphate. Eecent work by "Waynick^ and 

 Davis* has emphasized the necessity for inter- 



may be suggestive in connection with the 

 first point mentioned in this note. Three 

 series of nutrient solutions were prepared :° 

 (a) Solution used by the author. 

 (6) Shive's best solution, R5C2. 

 (c) Shive's solution diluted to 1/3 of its 

 concentration in 6. 

 In each case 15 barley plants were grown 

 for six weeks under favorable and uniform 

 conditions of sunlight. The containers were 

 of one liter capacity and only one plant was 

 grown in each bottle. The solutions were 

 changed weekly. Thus the total volume of 

 solution provided for each plant was consider- 

 ably larger than that used in most experiments 

 of this type. Iron tartrate was added twice 

 each week to all cultures. All the plants grew 

 at a uniform rate and there was no apparent 

 difference between the three sets at any time. 

 The initial composition of the three solutions 

 and the weights of the plants air dried were 

 as follows: 



preting the data obtained in plant culture ex- 

 periments with due consideration given to the 

 variability of plants. In the majority of 

 previous experiments this question has been 

 almost completely overlooked. 



During the course of an investigation on 

 certain phases of plant nutrition, an inci- 

 dental experiment has been carried out which 



ID. E. Hoagland, Science, N. S., Vol. XLIX., 

 pp. 360-362 (1919). 



2 D. E. Hoagland, Jour. Agr. Bes., Vol. XVIII., 

 pp. 73-117 (1919). 



3 D. D. Wayniek, Ann. Eep. College of Agr., 

 University of California, 1918-19, p. 67. 



* A. E. Davis, Univ. of Calif. Pub. in Agr. Sei. 

 (in press). 



J. W. Shive, Phys. Eesearehes, Vol. 1, pp. 

 327-397 (1915). 



It is evident that solutions a and 6 pro- 

 duced equally favorable growth within the 

 limits of error of this experiment, while the 

 smaller yield from c is not necessarily signifi- 

 cant, although in this case it is possible that 

 the total supply of nitrate was insufficient. 

 Thus in this experiment (a number of other 

 experiments not now reported lead to the 

 same conclusion) solutions of radically differ- 

 ent concentrations and salt proportions have 

 not affected the yield of the crop to any im- 

 portant extent. There is, however, no inten- 

 tion to give the impression that certain solu- 

 tions (possibly including those containing 

 large proportions of magnesium salts) may 

 not inhibit plant growth because of unfavor- 

 able physiological balance. The point which 



