510 EXPERIMENT STATION RECORD. [Vol.43 



and their suitability to fruit and vepotahle growing, sun-curing of fruits, dehy- 

 dration of vegetables, and production of flower and vegetable seeds. 



Carbon dioxid and plants, II, E. Rkinau (Chem. /Ay., ^3 {1919), Nos. 88, pp. 

 l',9-.',51; 91, pp. 469-^72; 9Jt, pp. Jt89-J,91; 97, pp. 509-512; 99, pp. 524, 525; abs. 

 in .Jour. Chcm. Soc. [London], 118 {1920), No. 687, 1, pp. 128, i2»).- Continuing 

 earlier work,' an account of which has been noted from another source (E. 

 !S. K., 31, p. 235), a critical review is given of the available data concerning 

 the amount of carbon dioxid in the air, its fluctuations, and its relation to 

 plant growth under natuial climatic conditions. 



A mathematical expression is devoloped which takes into consideration the 

 effect of both water and carbon dioxid on the growth of plants under sucli 

 conditions. "The differences in concentration of these substances within and 

 without the plant are regarded as differences of tensi(m, the value of wliicli ap- 

 pears to depend mainly on temperature and atmospheric humidity. Under 

 climatic conditions, the amount of assimilation by green plants is not pro- 

 portional to the absolute carbon dicjxid content of the air but to the difference 

 in tension. The internal pressure of carbon dioxid depends on the tem- 

 perature, with rise of which it increases, and also on the illumination, with 

 increase of which it falls. . . . The actual value of the carbon dioxid 

 tension difference depends on the capacity of the air to receive water vapor, 

 and therefore indirectly on the temperature, .-ind this is explained by the close 

 connection which exists between the utilization of the carbon, water, and salts 

 within the plant." 



The author believes that " the carbon dioxid content of the atmosphere is 

 regulated by the activity of terrestrial green plants and of the sea on the one 

 hand, and by that of humus (edaphon) on the other; this is rendered probable 

 by the extreme sensitiveness of plants to alteration in the tension of carbon 

 dioxid and by the fact that the action of green plants and edaphon is so 

 nicely balanced that the actual quantity of carbon dioxid in the atmosphere 

 is the expression of the dynamic equilibrium of the results of these two factors. 

 Consequently, the absolute carbon dioxid content of the atmosphere is not a 

 measure of the amount of carbon dioxid available for vegetation, but rep- 

 resents the proportion which can not be lessened by plants under average 

 conditions. It is conceivable that cases could arise in the open in which the 

 plant suffers from too little carbon dioxid; the agricultural aspect of this 

 possibility and the means of preventing it are discussed in the original paper, 

 as is also tlie beneficent effect of an increased concentration of carbon ([ioxid 

 on diseased plants." • 



The infiuence of crop rotation, green manuring, and the use of manures on 

 the carbon dioxid balance in soils is discussed as compared with that 

 of the continuous growth of cereals. The need of study on the rela- 

 tion of the character of the humus, temperature, moisture, and bacterial action, 

 to the production of carbon dioxid in the soil is emphasized. The author 

 attempts to explain why an increase of carbon dioxid in tlie air surrounding 

 plants promotes flowering and enables them to overcome injuries and diseases 

 more succe.ssfully. 



Monthly Weather Review {U. S. Mo. Weather Rev., 48 {1920), Nos. 3, pp. 

 127-190, pis. 19, figs. 22; 4, pp. 191-249, pis. 17, figs. 12).— In addition to de- 

 tailed summaries of meteorological, climatological, and seismological data anc 

 weather conditions for March and April, 1920, and bibliographical informatior 

 reprints, reviews, abstracts, and minor notes, these numbers contain the fol-j 

 lowing contributions: 



^Chem. Ztg., 38 (1914), No. 51, pp. 545-547, 



