NATURE 



493 



THURSDAY. SEPTEMBER 



^4, 1903- 



PLANT PHYSIOLOGY. 

 A Text-book of Plant Physiology. By George James 

 Pelrce, Ph.D. Pp. iv + 285. (New York: Henry 

 Holt and Co., 1903.) 



THE author's object is to present " the main facts 

 of plant physiolog-y and the saner hypotheses 

 regarding them, striving to express safe views rather 

 than to echo the most recent . . . and everywhere 

 trying to avoid giving the impression that the science, 

 or any part of it, has reached ultimate knowledge and 

 final conclusions." The standard adopted is to treat 

 the subject " less exhaustively than Pfeffer's ' Hand- 

 buch,' and more fully than Noll's section of the Bonn 

 t< \t-book." 



This, though doubtless an admirable object, is one 

 not easy to attain, and the result, it must be confessed, 

 is a book of unequal merit. As an instance of the 

 author at his best may be mentioned the section (p. 72) 

 on " Root-tubercle Plants." The six pages devoted to 

 the matter give a clear and readable account which 

 should suflice for the needs of the moderately elemen- 

 tary student. On the other hand, the final section of 

 the same chapter — that on the ash constituents — is un- 

 satisfactory. The student gets from it neither a clear 

 conception of what is meant by the essential con- 

 stituents of the mineral food-supply nor a knowledge 

 of the more interesting details. For instance, the 

 reader is not even directed by references to Schimper's 

 work on oxalates in reference to the assimilation of 

 nitrates. It is possible that the author does not con- 

 sider this to be one of the "saner hypotheses," but 

 in that case it might have been discussed with a 

 caution. 



When the author deals with photosynthesis the re- 

 sult is better, and there is much to interest the reader. 

 The chief fault in his presentment of the subject is 

 that he docs not fully face the relation between the 

 photosynthetic activity of different parts of the spec- 

 trum and the absorption bands of the chlorophyll 

 spectrum. This is a fundamental point, and should be 

 discussed in a treatise such as the present. 



Dr. Peirce's style might here and there be mended. 

 Take, for instance, the following sentence (p. 43), with 

 which photosynthesis is introduced : — 



" The source of carbon for all organisms except the 

 nitrogen bacteria and plants containing chlorophyll 

 or its apparent equivalent physiologically, bacterio- 

 purpurin, is, directly or indirectly, these colour-contain- 

 ing plants." 



The chapter (p. 103) on the " absorption and move- 

 ment of water, &c.," is not uniformly good. The 

 student will learn from it if he has the gift of picking 

 out what is best, but we fear that he will not get to 

 the root of the matter. This p?irt suffers especially 

 from the author's plan of not in general describing 

 methods of research. It seems to us impossible to 

 give a clear or interesting view of the problem of water- 

 NO. 1769, VOL. 68] 



transport without a more direct appeal to experiment- 

 Thus, in the section on *' the means of transfer of 

 nutrient solutions " (pp. 1 16-124), ^^'^ miss an account 

 of the fundamental fact that a cut branch in a glass 

 of water is a self-regulating mechanism, in which 

 absorption is practically equal to loss by transpiration. 

 It is only at p. 141 that we get the idea briefly stated 

 without proof. 



Chapters v., vi. and vii. are respectively devoted tO' 

 growth, irritability, and reproduction. It is doubtless 

 a difficult matter to give an adequate account of 

 irritability in such a book as the text-book before us, 

 but when full allowance has been made for such 

 difficulty, there remains a good deal to which excep- 

 tion must be taken. 



We miss a general statement of the widely accepted 

 view according to which a plant (like an animal) is 

 guided by certain definite irritabilities strictly com- 

 parable to the senses of animals.* It seems to us 

 clear that Dr. Peirce's views do not harmonise with the 

 modern conception of irritability. Thus, in speaking 

 (p. 213) of heliotropic curvatures, he asserts that the 

 bending of a stem towards the light is the mechanical 

 result of the increased growth-rate on the shady side 

 of the stem. He thus ignwes the well-known fact 

 that the growth-rate of apheliotropic organs is also 

 increased by darkness, a result fatal to his point of 

 view. It is depressing to find this way of looking at 

 heliotropism (which we had hoped was dead and 

 buried) once more to the fore. 



In some matters of fact we cannot agree with the 

 author's statements. Thus at p. 214 we read :— 



" So much more does gravity influence the directior» 

 of growth of roots that the influence of light is 

 scarcely apparent until all parts are uniformly sub- 

 jected to gravitation by means of the clinostat." 



The student who has grown mustard seedlings in 

 a glass of water and exposed them to one-sided 

 illumination will read the above statement with sur- 

 prise. Elsewhere the author's treatment of the action 

 of light and gravitation is singularly confused, if not 

 downright wrong. Thus (p. 214) we read that the 

 direction of growth of leaves is a resultant of two 

 forces, gravity and light, in Illustration of which he 

 describes leaves assuming a normal light position 

 while slowly rotated on the clinostat, the whole point 

 of the experiment being in reality to prove that the 

 normal light position may be assumed in response to 

 light alone, and not as a compromise between sensi- 

 tiveness to light and gravitation. 



On the whole, we think the part on irritability 

 suffers from the attempt to crowd too much into the 

 available space. The student would gain if less detail 

 were attempted, and a simpler, broader treatment 

 adopted. 



What we have said of one section may be perhaps 

 applied to the book as a whole. A reader with a power 

 of selection will be able to make use of It, and he will 

 find much that is not to be obtained from ordinary 

 English text-books. F. D. 



1 Brief and partial statements occur at pp. 206 and 207. 



Y 



