632 EXPERIMENT STATION EECORD. IVoL 37 



The influence of some organic substances on plants, I, G. CJiamician and 

 C. Ravenna (Atti R. Accad. Lined, Rend. CI. Sci. Fit., Mat. e Nat., 5. ser., 26 

 {1917), I, No. 1, pp. 5-7). — This article, whicb is related to previous work (E. 

 S. R., 36, pp. 329, 432) and la regarded as suggestive of further studies on a 

 larger scale, discusses briefly the effects on plant growth of several orgaulc 

 substances, including mandelic nitrlle, nlcotin, strychnin, caffeln, and morphin. 



Quantitative experiments demonstrating the mechanism of the inhibition 

 of growth, J. LoEB {Proc. Soc. Expt. Biol, and Med., lit (1917), No. 7, pp. ISl, 

 132). — The author has studied by a quantitative method the laws of inhibition, 

 several reports regarding which have been noted previously (B. S. R.. 34, p. 

 730; 35, p. 820; 37, pp. 324, 325). Proceeding upon the hypothesis of Inhibition 

 ^f growth by one organ in relation to another by the removal of material 

 necessary for growth, and upon the expectation that if such were the case the 

 total mass of shoots produced by a leaf in a certain time would be approxi- 

 mately the same regardless of their number, he claims to have found that this 

 is true to a surprising degree of exactness. The quantitative data so obtained, 

 as briefly Indicated In the statement, are relied upon to furnish the basis of a 

 chemical theoi-y of regeneration. 



Studies in permeability. — IV, The action of various organic substances on 

 the permeability of the plant cell, and its bearing on Czapek's theory of the 

 plasma membrane, W. Stiles and I. Jobgensen {Ann. Bot. [London], 51 

 [1917), No. 121, pp. 47-76, figs. 15). — The authors have carried forvvard the 

 series of studies the last noted of which was contributed by Mildred Hind 

 (E. S. R., 36, p. 433). The present contribution relates partly to tests made 

 by the author as bearing upon Czapek's theory of a plasma membrane, earlier 

 (E. S. R., 24. p. 137) and later reports on which are discussed, with a statement 

 of alleged reasons for the rejection of sume views held by that author. 



The method employed Is here describwl in more detail than in the article 

 previously noted (E. S. R., 3i5, p. 224). with an account of its supposed ad- 

 vantages over the methods formerly used, such as greater exactness and more 

 general applicability. 



It is stated that with each organic substance a higher rate of exosmosls cor- 

 responded to a higher concentration of the substance employed. Equlmole- 

 cular solution.s of different substances do not bring about the same exosmosls. 

 The rate of exosmosls produced by a solution is not a function of its surface 

 tension alone. A concentration below which exosmosls of electrolytes could not 

 take place was not found. In the attempt to deduce a mathematical time-rate 

 expression for exo.smosls, it was found that the equation expre.ssing the results 

 of actual experiments exactly resembled that expressing theoretical considera- 

 tions. 



The osmotic concentration of the sap of the leaves of mangrove trees, J. A. 

 Harris and J. V. Lawbenck {Biol. Bui. Mar. Biol. Lab. Woods Hole, 32 {1917), 

 No. 3, pp. 202-211). — Presenting the results of a series of determinations of the 

 leaf tissue fluids of Avicennia nitida, Rhizophora mangle, and Laguncularia 

 racemosa on the southern shore of .Jamaica and in southern Florida, the 

 authors state that the concentration of these fluids is relatively high through- 

 out, the range as noted lying between the limits of 20 and 50 atmospheres. 

 Avlcennia apparently developed a much higher concentration than the other 

 species in the same envlroinnent. 



The orig:in of chromoplasts and the mode of formation of xanthophyll 

 and carotin pigments, A. GmuJEKMONO {Compt. Rend. Acad. Sci. [Pnrii], 16^ 

 {1917), No. S, pp. 2S2-235). — Giving a r^sumg of related studies to date, the 

 author states that the various forms in which pigments may appear can be 

 arranged under three general heads. These are according as to whether the 



