NA TURE 



THURSDAY, SEPTEMBER 2S, 1893. 



THE PHYSIOLOGICAL PAPERS OF 



PROF. SACHS. 



jesammellc Abhandlungen iiber PJlanzen-physiologic. 



Von Julius Sachs. 2 vols., with 126 woodcuts and 10 



plates. (Leipzig, 1892-3.) 



hPHIS excellent collected edition of Prof. Sachs's 



j-»- chief contributions tc the physiology of plants will 



fe welcome to all botanists. The author in his preface 

 xplains the very sufficient reasons which have led him 

 io publish this collection, and the principles which have 

 Juided him in the choice of papers. He has not thought 

 necessary to reproduce all his physiological treatises, 

 ut has more especially aimed at selecting such as deal 

 'ith matters of fact rather than theory, while some which 

 e considers to be sufficiently well known already are 

 mitted. 



Such a collection is a great help to the reader, and es- 

 iecially so when it is compiled by the author himself In 

 lis case we do not merely obtain a series of isolated 

 apers, but have the further advantage of learning the 

 juthor's mature view of the relative importance of his 

 kvn researches. 



! Many of the papers have been abridged, and some are 



hly given in abstract. In many cases notes have 



ben added, which are not the least interesting part of 



le work, as they often indicate the author's latest views 



't the questions at issue. 



To review adequately a collection of Prof Sachs's 



siological treatises would be to write the history of 



■table physiology from 1859 onwards. Such an at- 



iiipt is out of the question ; only a very short sketch 



' the contents of this book can be given here. 



The selected papers, 43 in number, are arranged, ac- 



rding to subject, in nine groups ; within each group the 



jder observed is chronological. The first volume con- 



'ins works concerned chiefly with the chemical and 



lysical phenomena of vegetation, while those contained 



the second volume are on growth, cell-formation, and 



ritability. 



The first section contains essays on the action of heat 



1 plants. The first, published in 1S60, is on the effects 



'' ost. The observations described will be remembered 



ill readers of Prof Sachs's text-book. There is much 



om for further research on the effects oi low tempera- 



les on various plants, and the subject is obviously of 



tical as well as of physiological interest. 



ther papers in this group are on the dependence of 



aination on temperature, on transitory rigidity in ir- 



1 able organs, on the superior limit of temperature as 



aecting vegetation, and on the influence of temperature 



11 the formation of chlorophyll. All these investigations 

 e of fundamental importance ; the same perhaps can 

 ■ cely be said of the last paper in this part, " On Emul- 

 I Figures and the Grouping of Swaim-spores in 

 ler," which is merely concerned with a possible 

 rce of error in observations on the movements of 

 ellular organisms, 

 liie succeeding section, on the action of light on plants, 

 )cludes some of the best known of the author's re- 

 NO. I24S, VOL. 48] 



V 



searches, the most important perhaps being that on the 

 effect of light of different colours on assimilation and 

 growth. It is a little disappointing, however, to find no 

 reference in the notes to the more recent and exact work 

 of Timiriazefif, Engelmann, and others. The latest 

 published paper in this section, " On the Action of the 

 Ultra-violet Rays on the Formation of Flowers " (1883 

 and 1S86), is probably less familiar to physiologists than 

 the others. In this. Prof. Sachs brings forward evidence 

 to show that when, in the case of a green plant, the 

 ultra-violet rays alone are excluded, the development of 

 flowers is hindered, though otherwise the plant grows 

 normally. The conclusion which he arrives at is that 

 the ultra-violet rays produce, in the green leaves, the 

 " flower-forming substances." 



The third group of [papers, on chlorophyll and assimi- 

 lation, is certainly among the most important in the 

 collection, for by means of these researches the author 

 first proved that the chlorophyll corpuscle is the organ 

 of assimilation, a fact which forms the basis of the whole 

 physiology of nutrition in plants. The investigations, 

 dating from 1S62, by which Prof. Sachs showed that 

 starch appears in the chlorophyll corpuscles as a result 

 (though, as we now know, not an immediate result) of 

 assimilation, are of special interest at the present 

 moment, in view of the new light recently thrown on this 

 whole subject by the work of Messrs. Brown and 

 Morris. 



Later papers in the same section are those " On the 

 Activity of Nutrition in Leaves" (1884), and on "The 

 Treatment of Chlorotic Plants " (1SS8). The former is de- 

 voted chiefly to the determination of the energy of assi- 

 milation in the leaves of various plants. The latter is the 

 only paper in the collection written with a " purely 

 practical " object, namely to teach the most convenient 

 and effective method of applying iron salts as manure 

 to plants which, from want of iron, fail to develope their 

 chlorophyll. 



The fourth section includes the work on the move- 

 ments of water in plants. Among other researches of 

 importance, we here find the well-known treatises '' On 

 the Ascending Current of Sap in Transpiring Plants " 

 (1877-8) and "On the Porosity of Wood " (1877-9). The 

 former contains the author's classical determinations of 

 the rate of ascent of the sap, by means of the Lithium 

 spectroscopic method, while in the latter his famous 

 " imbibition theory," according to which the water rises 

 in the substance of the lignified cell-walls, is developed. 

 This theory is no longer accepted by physiologists, but 

 the author justly points out that the facts given in the 

 paper maintain their value quite independently of the 

 truth of his theoretical conclusions. 



The papers of the fifth group, on the behaviour of the 

 constructive materials during growth, are all of early 

 date (1859-63}, and the author regards their interest as 

 being mainly historical. To us they seem to be among 

 the most attractive in the collection. Most of them 

 relate to the phenomena of germination, and especially to 

 the changes undergone, during that period, by the reserve 

 food substances, while many facts of morphological and 

 histological interest are also told us. 



Going on to the second volume, we find in the sixth 

 section of the work the author's researches on the subject 



Z 



