730 EXPERIMENT STATION RECOKD. [Vol.38 



The results up to this time on the different plants named leave the question 

 regarding the influence of the chlorin ion and chlorids upon plants in a very 

 complicated and unsatisfactoi-y condition, apparently not admitting of any gen- 

 eral statement. It is thought that the effect of chlorin upon any given plant 

 depends upon the nature of the plant and the soil and climatic conditions. 

 Progress in the interpretation of the climatic complex as a whole may be re- 

 quired. More complete experimental control of the very numerous conditions 

 that make up the environment of the plant is also essential, as it is the summed 

 or integrated effect of all of these that is registered by plants in growth and 

 crop production. 



A study of salt proportion in a nutrient solution containing chlorid, as 

 related to the growth of young wheat plants, S. F. Tkelease {Johns Hopkins 

 Univ. Circ, n. ser., No. S {1917), pp. 222-225). — In the experiments of which 

 this is a preliminary report, the chlorin ion was added as potassium 

 chlorid to nutrient solutions already containing all the essential elements 

 usually absorbed by plant roots, in the form of the salts calcium nitrate, 

 magnesium sulphate, monopotassium phosphate, and . ferric phosphate. The 

 total concentration of the solutes corresponded to an osmotic pressure of about 

 1.6 atmospheres at 25° C, and the relative proportions of the salts were used 

 in aU possible ways by making additions of one-tenth of this total concentra- 

 tion, each complete set including 84 different solutions. The data obtained are 

 discussed in connection with the findings and views of other investigators. 



It was found tliat with combinations of the three salts monopotassium phos- 

 phate, calcium nitrate, and magnesium sulphate, or these with potassium 

 nitrate or with potassium chlorid, the same growth is obtained if the best pro- 

 portions of the salts are used in each case. This generalization is thought to 

 have an important bearing upon the whole problem of physiological balance in 

 nutrient solutions, and to furnish what may prove to be important suggestions 

 bearing on our general conceptions of conditional control and conditional optima 

 for plant activities. 



The relation of the concentration of the nutrient solution to the growth. 

 of young wheat plants in water cultures, S. F. Trelease (.Johns Hopkins 

 Univ. Circ, n. ser.. No. S {1917), pp. 225-227). — These experiments differed 

 somewhat from those above noted. The salt proportions were the same in all 

 different solutions of each series, but the solutions differed from each other in 

 total concentration. 



It is stated that transpiration and dry weight showed an approximately 

 linear relation to the concentration of the medium above the optimum and 

 that these decreased with an increase in concentration. The optimum con- 

 centration for dry weight of tops was altered from 1.6 to 4.5 atmospheres by 

 changing the proportions of the four salts used in two of the series. The 

 omission of potassium chlorid did not change the relation between growth and 

 concentration. 



The effect of renewal of culture solutions on the growth of young wheat 

 plants in water cultures, S. F. Tbelease and E. E. Free {Johns Hopkins Univ. 

 Circ, n. ser., No. S {1917), pp. 227, 228). — Reporting detailed results of experi- 

 ments on the growth of wheat plantlets in the nutrient solutions found by 

 Shive (E. S. R., 36, p. 328) to be the most suitable for the production of dry 

 weight of tops in wheat, the author states that frequent changing of the solu- 

 tion increased the yield. Daily change produced marked improvement and 

 continuous flow was even more beneficial. Marked injury was observed when 

 the solution was changed as infrequently as every two weeks. Shaking with 

 bone black improved the solution slightly but did not correct in any great 



