igig] 



CURRENT LITERATURE 



177 



results on wheat in the following table, showing the mean molecular proportions 

 of the 3 component salts and the ionic ratios for the culture solutions giving 

 the best and the poorest growth of wheat during the different periods of 

 development. They promise a full discussion of data with the publication of 



results of experiments, now being carried on at the Maryland Experiment 

 Station on the nutrient requirements of soy beans and buckwheat. 



.\11 this work indicates that Sachs, Knop, and others had not nearly 

 exhausted the subject of desirable nutrient solutions for water and sand cul- 

 tures, but that we still have much to learn. The concentration of the nutrient 

 salts used in these solutions are far above those existing in the general soil 

 solution, and upon the whole the immediate significance of this work in prob- 

 lems of soil fertility is not evident. In the soil the dissolving power of well 

 developed root hairs in contact with nutrients of low solubility introduces a new 

 and important feature. It must be stated, however, that Hibbard's work 

 offers indications of an important bearing of this method on questions of soil 

 fertility. — Wm. Crocker. 



Respiration and age of plant organs. — Nicolas" has studied the respira- 

 tion of very young leaves and leaflike structures in comparison with that of the 

 corresponding fully developed organs taken from older parts of the same plants. 

 In a few cases he included also a comparative study of the respiration of sections 

 of the stem or branch bearing the young and old leaves. His material was 

 selected from 15 diflferent species, including annuals, biennials, and perennials. 

 The studies were conducted by the method of confined atmospheres in absence 

 of light at temperatures from 15 to 24° C, the gas analysis being made with the 

 Bonnier-Mangin apparatus. Respiratory intensities were calculated on the 

 basis of the fresh weight of the materials used. The "internal respiration" 

 also was determined in a few cases, using hydrogen atmospheres. Respiratory 

 quotients CO2/O2 and the ratio I/N between "internal respiration" and normal 



" Nicolas, G., Contribution a I'etude des variations de la respiration des vege- 

 taux avec I'age. Rev. Gen. Botanique 30: 214-225. 1918. 



