1919] AGRICULTURAL BOTANY. 425 



of a possible continuance of hostile control of the great potash deposits. The 

 opinion is expressed that when potassium is not available in sufficient quantity 

 some of the physiological functions normally performed by that element may 

 be assumed by sodium. Regarding the nature <>f « h«s«- functions, several sug- 

 gestlons are given. 



A comparative study of salt requirements for young and for mature buck- 

 wheat plants in sand cultures, J. W. Shxve [Soil Sot., 8 (1918), No. I. i*p. 1S2, 

 flga. S). — This is a report of work done with sami cultures on the salt require- 

 ments during two different developmental periods <>f buckwheat plants, cor- 

 responding to that reported with solution cultures (E. S. EL, .".:•, p. T.".J). The 

 results obtained from the two series of studies are compared in this paper. The 

 sand cultures were supplied with nutrient solutions of salts having the same 

 range of concentration as in the work previously noted. 



The relation of growth rates to variations in the osmotic proportions of the 

 solutions supplied to the sand cultures differs markedly for the two develop- 

 mental periods, whether this be judged by top or root growth, transpiration, or 

 water requirements. 



Factors determining character and distribution of food reserve in woody 

 plants. E. YV. Sinnott (Bot. Qoz., 66 (WIS), No. 2, pp. 162-175, Jigs. 2).— A study 

 of the minute deposits of food materials in twigs and young branches of different 

 plants shows that in winter starch is to be found more commonly in regions 

 remote from centers of conduction and in eells having thick walls with small 

 pits, while fat is most abundant in and near the phloem, close to vessels, and in 

 cells with thin or unlignified walls or large pits. These facts indicate that the 

 character of the food reserves In any cell depends primarily upon the readini 

 or difficulty with which water or solute reaches the cell, fat appearing in the 

 former case, starch in the latter. This suggests that differences in the type of 

 food reserve may be due to differences in water content of the various storage 

 cells (resulting in modification of enzym activity) or to differences in the ease 

 with which enzyms have access to the storage cells. 



The nature and role of mitochondria in vegetable cells, A. Grin n bmobtd 

 (Compt. Rend. Soc. Biol. [Ports], 80 (1917), No. 19, pp. 917-024. pis. 2).— The 

 author replies to some objections offered to his views, as set forth in connection 

 with his various contributions, regarding the characters and significance of 

 certain bodies or structures said to be present in the cells of both animals and 

 plants. 



The formation of nitrites from nitrates in aqueous solution by the action 

 of sunlight, and the assimilation of the nitrites by green leaves in sunlight, 

 B. Moore (Proc. Roy. Soc. [London], Ser. B, 90 (1918), No. B 621. pp. 158-167).— 

 The author considers the assumption to be entirely untenable that the green 

 cell, complex and highly organized as it now is, constituted at the dawn of life 

 the only agency capable of utilizing light energy so as to produce a gain in 

 chemical energy. He emphasizes the importance of a study of the action of 

 light on organic substances present in air and water and supposedly capable of 

 being acted upon eudothermically by light so as to produce more complex com- 

 pounds of organic character. A continuation of experimentation previously 

 reported (E. S. R., 33, p. 627) is said to show that air. rain, and dew invaria'hly 

 contain a mixture of nitrites and nitrates, the former ordinarily tending (on 

 their being kept together) to pass over into the latter, and the process being 

 reversed as a result of insolation or exposure to artificial light of short wave 

 length. The inference is that both these nitrogen compounds occur in atmos- 

 pheric air, and this is said to have been supported by experiments referred to. 

 The nitrogen percentage requirement Cor plants is said to average not abow B 

 per cent of the carbon assimilation requirement. 



