The Role Of Diffusion And Osmotic Pressure In Plants

PREFACE WITH the ever-increasing tendency to regard an organism as a compIex of physical and chemical processes which may one day be analyzed and understood, there has necessarily gone hand in hand a tendency toward more and more accurate and quantitative investigation of the physics and chemistry of the cell itself. Among the various groups of physical and chemical phenomena that have been found to play important rdes in the life-process, and wlzich, therefore, have been interrogated for answers to physiological questions, none has stood out within the past few years as more fundamentally important than those connected with diffusion and osmotic pressure. This field has thus far only been touched upon, and it would seem, judging from researches which have recently appeared, that the best and most far-reaching work therein is probably yet to come. The present volume will deal with the past and present of diffusion and osmotic pressure from the standpoint of plant physiology. It has a double rnison detre. First, it was felt that there was need of some direct and not too exhaustive account of the essential physical facts and theories of the subject. The interest of the physical chemist here has lain mainly in the light which these phenomena have been able to throw upon the ultimate nature of matter and upon electrolytic processes. I t has thus been difficuIt for the student of physiology who is not at the same time well versed in physical chemistry to obtain the information required for the prosecution of work in this field. Secondly, it seemed desirable to bring together in a genergl review the literature of this subject in its biological aspects, so that the promising and unpromising points for future research might become ix more at parent. Tlie volun e --ill thus naturally fall into f 7 P 1 a rts, tlie first dealing with the 1 urcly pliysical aspect of tlicsc plienoniena, and the second attempting to present in a niore Or less nriifiecl whole the 1 hyvsiologicnl results t-liic. 11 llnrc so far appeared in this connec. tion, togethcr with tlieir hearing ,. upon each ot1ic. r and upor1 tlie vital problem as n v-hole. C1inl tcr IT of Part I1 was presented to tlie F lculty of tlie 0gdc. n Graduate School of Science of the rniversity of Cliicago in carlclitlacy for the doctors degree in 1 01. Tl eai ltlior 7s-islies liere to express his thanks to Professor C. R. Barnes, of tliis laboratory, and to Professor Jacclues Loeb. of tlle Hull Physiological Laboratory, for much valuable aid. Professor Barnes Eias kindly read tlle man zscript and has matle many suggestions. The author alone ip, however, responsible for whateuer new departures are to be founcl in the book. B. E. L. THEH ULLB OTASIC. LL HORATORP, The Unisersity of Chicago, October 1,1902. TABLE OF CONTENTS PART I. PHYSICAL CONSIDERATIOXS CII PTC I. R JI ittflr an 1 Its States - - - 3 I. 1 unda1nc nt Till1 c. oric. s of the Nature of Natter. L Thr Altomic. Theory. 71 The Kinetic Theory. 11. The Thrcxc States of Matter. CHAP 1 1 E . R D iffr siona ncl Diffusion Tension - - 9 I. Gases. U Silllplc Gnhcs. 1, Mixed Ciaach. 11. Liquidh. u Sirnple Liquids. b Mixed Liquids. 111. Solids. a Simple Solids. 71 Diffusion of Two Solids. CHAPTE 1 R 11 . Liquid Solutions - - 16 I. Liquids in Lirluids. Ir. Gases in Liquids. rrr. Solids in Licluitls. rv. Terminology for Solutions of Differing Concentration. CHAPTE IV R . Ionization-. - 23 I. Of Gases. 11. Of Solutes in Liquid Solutions. CHAPTE T R . Osmotic Phenomena - - - 25 I. Oyrnotic Pressure of the Solute. a Kon electrolytes. b Electrolytrs. C Colloids...