w\ 



128 EXPERIMENT STATION EECORD. [Vol. 36 



Studies on the medium of exchange between roots and soil and among 

 tissues in the plant, P. MAzfi (Ann. Inst. Pasteur, 29 {1915), No. 12, pp. 601- 

 632; 30 (1916), No. 3, pp. 117-140, figs. 3). — Having continued studies previously 

 noted (E. S. R., 31, p. 221), the autlior states that the mechanism of absorp- 

 tion of nutritive substances from natural or artificial solutions does not in- 

 clude osmosis, the factors apparently operative in the introduction of nutri- 

 tive substances into circulation being the motility of protoplasm and molecular 

 attraction. The exchanges are possible when the nutritive medium contains 

 all the material necessary to the plant in definite concentration. Incomplete 

 solutions and distilled water introduced directly into the vascular bundles behave 

 as toxic agents. Plasmolysis should be regarded as a phenomenon of coagula-. 

 tion. Osmotic action does not occur between living cells and external media. 

 Absorption of sap is regulated by the chemical activity of the plant. Such 

 phenomena as sap pressure,, bleeding, and loss of turgescence are expressions of 

 variation in the pressure within the plant, resulting from want of equilibrium 

 between absorption and transpiration. Phototropic orientation in the stems is 

 due to inequalities of pressure caused by unilateral illumination. Circulation 

 of elaborated sap is assured by the turgescence in assimilating cells, which is 

 periodic, as is sap movement. 



It is claimed, in brief, that exchanges between plant and medium and among 

 plant tissues are brought about by the play of mechanical factors, among which 

 the njotility of protoplasm predominates by reason of the part it plays in the 

 control of permeability. 



The exchange of ions between the roots of Lupinus albus and culture 

 solutions containing three nutrient salts, II. H. True and H. H. Baktlett 

 {Amcr. Jour. Dot., 3 {1916), No. 2, pp. 1^-57, figs. 3). — In continuance of pre- 

 vious accounts of work with L. albus (E. S. R., 34, p. 224), the authors report 

 studies dealing primarily with mixtures of three salts. Two groups of experi- 

 ments are reported, one employing the nitrates of potassium, calcium, and mag- 

 nesium, the other employing monopotassium phosphate, calcium nitrate, and 

 magnesium sulphate, each experiment including 36 cultures, each with a con- 

 centration of 140 NX 10"^. 



It is stated that in general seedlings of L. aJbus absorb more salts from mix- 

 tures of potassium, calcium, and magnesium nitrates than from equally concen- 

 trated solutions containing one or two of these salts. The solutions of the 

 three nitrates found most favorable to absorption were much inferior to cor- 

 responding solutions in which the three anions, H2PO4-, NO3-, and S04=. 

 were present. The roots absorbed about 50 per cent of the salts from the best 

 solutions of the mixed nitrates and 85 per cent from those of the three anions. 

 In solutions of the mixed nitrates, as in those of the other compounds named, 

 the best absorption occurs when no single ion is greatly in excess, although 

 within a very wide range of variation in proportion the roots absorb with almost 

 equal efficiency. 



The antagonistic action of salts in plants, J. G. IMaschhaupt {Vcrslag. 

 Landbouick. Onderzoek. Rijkslandbouivprocfstat. [Netlierlnnds], No. 19 {1916), 

 pp. 1-60, pis. 5, fig. 1). — This is largely a critical discussion of findings and 

 views on the antagonism of salts in nutritive media, listing over 60 contribu- 

 tions on the subject. 



Immobility of iron in the plant, P. L. Gile and J. O. Carrero {U. S. Dept. 

 Agr., Jour. Agr. Research, It {1916), No. 2, pp. 83-81).— Ka a result of experi- 

 ments at the Porto Rico Experiment Station with rice grown in nutrient solu- 

 tions, the authors have concluded that iron is not transferred from leaf to leaf 

 under conditions where the plant is insufficiently supplied with iron. It ia 



