NATURE 



00' 



THURSDAY, JANUARY 21, 1909. 



Vl.XNT PHYSIOLOGY AND ECOLOGY. 

 i'hiiit Physiology and Ecology. By Prof. F. E. 

 Clements. Pp. xv+315; 125 illustrations. (Lon- 

 don : A. Constable and Co., Ltd., 1907.) Price 

 105. 6(i. net. 



rHE task of summarising the principles of ecology 

 and other branches of botany concerned with the 

 relation of plant to environment is one with which 

 teachers are confronted at the present time. Prof. 

 Clements in this book outlines a course which he has 

 carried out in a session with second-year students. His 

 views on vegetation as an " organism " are already 

 known from " Research Methods in Ecology " and 

 other publications. The present book, briefly stated, is 

 an attempt to graft on to " Research Methods " the 

 ph\siology of Sachs and Pfeffer and the ecology of 

 \\"arming and Kerner. The tree shows signs of one day 

 being a symmetrical organism, but at present the traces 

 of the grafting are somewhat conspicuous. Prof. 

 Clements has all along taken up his standpoint with- 

 out much consideration for the traditions of European 

 schools ; yet anything he writes is worth careful con- 

 sideration. " Research Methods " was distinguished 

 by such a marked disregard for principles admitted in 

 Europe that it provoked much criticism ; one, there- 

 fore, turns to the new book curious to see what the 

 last three years have brought about. 



The opening chapter is a.xiomatic, therefore im- 

 portant. The author's conception of physiology is 

 given in his own words. " A plant is an organism 

 capable of nourishing itself under the control of ex- 

 ternal conditions, and of modifying its form and struc- 

 ture in accordance with this fact." " The proper 

 task of physiology is the study of the external factors 

 of the environment or habitat in which the plant lives, 

 and of the activities and structures which these factors 

 call forth." " The former are causes, the latter 

 effects." "The sequence of study is consequently 

 factor, function, and form." " Physiology was origin- 

 ;illy understood to be an inquiry into the origin and 

 nature of plants." "This is the view that pervades 

 the following pages, and in accordance with this the 

 >ubj'ect-matter of ecology is merged with that of 

 physiology." A stimulus is defined as " any factor 

 of the habitat that produces a change in the functions 

 of a plant." The real test of a stimulus is " fur- 

 nished by the plant, since the presence of a stimulus 

 can only be ascertained by the response made bv the 

 plant." Stimuli are grouped " with respect to the 

 force concerned." " The factors of a habitat are 

 water, soluble salts, humidity, light, temperature, 

 wind, soil, pressure, physiography, gravity, polarity, 

 and biotic factors." "Certain of these, namely, soil, 

 physiography, pressure, and biotic factors, can act 

 upon plants only through the action of other factors, 

 as a rule." This grouping together of all the factors 

 of the habitat as stimuli, in " Research Methods," 

 evoked the criticism of physiologists accustomed to 

 distinguish between work which is the direct outcome 

 NO. 2047, VOL. 79] 



of energy flowing in from without (transpiration and 

 photosynthesis), and work done as the equivalent of 

 potential energy, the conversion of which is set 

 going by inflowing energy (" New Phytologist," iv., 

 p. 234). Commenting on this distinction between 

 tonic and stimulatory action. Prof. Clements says : — 

 " a careful analysis of these two processes shows that 

 at the bottom they are essentially the same," and differ 

 only in degree. He also adheres to his earlier 

 views on the nature of response. Adjustment is 

 " functional response " where " reactions to stimuli 

 are functional only." .Adaptation is " structural re- 

 sponse " where a structural change also occurs. 

 "Adjustment may be expressed in the movement of 

 parts or organs ... or in growth or modification of 

 structure." " Adaptation comprises all structural 

 changes resulting from adjustment." 



These are fundamental principles of this book. Five 

 chapters (pp. 7-143) are concerned with adjustment to 

 water, light, temperature, and gravity; two (pp. 144- 

 184;) with adaptation to water and light. The chapter 

 (ii.) on " the water of the habitat " is already familiar 

 to readers of " Research Methods." The difficul- 

 ties of a beginner in field-work are not quite fully 

 realised, but with the aid of this chapter and the ex- 

 periments suggested he should be able to grasp the 

 objects of this line of investigation. The system em- 

 ployed in framing the chapters on adjustment is to 

 give a general — often a very general— outline of the 

 structure of the organs concerned and to add experi- 

 ments on function. This part of the work lays itself 

 open to frequent criticism, and most instructors, while 

 appreciating the suggestions, will improve along their 

 own lines. Adjustment to water is subdivided under 

 topics; " absorption" includes structure and function 

 of the root and the principles of imbibition, osmosis, 

 diffusion, and turgidity ; "transport" includes brief 

 descriptions of stem structure and the upward move- 

 ment of water; " transpiration " deals with leaf struc- 

 ture and function. One must admit that it is no easy 

 task to give a condensed account of these processes, 

 but a clear conception of them is essential, even to the 

 ecologist, and their treatment here does not satisfy. 

 Either the student has become familiar with elementary 

 anatomy and physiological experiments during an 

 earlier period of his course, or he ought to know more 

 than is given in these pages. Many phrases suggest 

 a first primer; thus, "the fibrovascular system is 

 usually in the form of an interrupted circle of bundles 

 strung like beads upon the ring of cambium." So 

 also do some e.xperiments ; thus, osmosis is demon- 

 strated by a thistle funnel and parchment (no other 

 experiment), and turgidity with a piece of " dialyser 

 tubing." The ecologist may be sadly in need of the 

 more intimate and exact methods of the physiologist, 

 as Prof. Clements says, but this deficiency is not re- 

 moved by acquaintance with a few elementary experi- 

 ments, and the ecologist should be induced to follow 

 the latest the laboratory physiologist is doing. One 

 cannot help thinking that the author has not taken this 

 part of his work seriously, but has thrown out as sug- 

 gestions what first came to mind ; even in the proof- 



N 



