242 



NATURE 



[July 14, 1904 



The rate of disintegration of the radio-active bodies 

 is also independent of their state of chemical com- 

 bination, which indicates that the radio-active pro- 

 perties belong entirely to the so-called atom of the 

 radio-active element present, and are not communicated 

 to the other atoms present in the compound. 



It thus appears that the atoms of the so-called 

 elements contain an immense store of energy, and this 

 discovery leads to interesting possibilities which Prof. 

 Rutherford discusses in connection with the heat 

 supply of the sun and earth, and other heavenly bodies. 

 If the sun and earth draw their heat- supply from this 

 store, then it is possible that the present rate of 

 emission may have been going on for vastly longer 

 ages than those hitherto supposed possible, longer 

 even than the ages demanded by geologists for the 

 completion of the processes of formation of the earth's 

 crust. 



Exception may be taken to the terminology adopted 

 in some parts of the book. For example, the product 

 of decomposition of the radium emanation which is 

 deposited on solid bodies is referred to as '' emanation- 

 X." It would probably be better to reserve the term 

 emanation for radio-active gases ; but at the same 

 time, it must be admitted that " emanation-X " is a 

 better name than "induced radio-activity." 



The arrangement of the matter and its treatment are 

 throughout admirable. 



Mr. Soddy's book on radio-activity contains an 

 excellent and interesting account of the subject. The 

 arrangement of the matter and point of view adopted 

 are very similar to those in Prof. Rutherford's book, of 

 which Mr. Soddy's is practically an abridged and 

 slightly popularised edition. 



Messrs. Levy and Willis's book on radium is sup- 

 posed to be of a popular character, and contains an 

 account of many of the properties of radio-active 

 bodies. The arrangement of the matter cannot be 

 commended, and the authors' scientific knowledge does 

 not appear to have been sufficient for the task they 

 have undertaken. Facts and results which it is 

 suggested might be obtained if looked for are mixed 

 up in a manner calculated to confuse the reader; there 

 are besides many inaccurate statements. It is difficult 

 to see what useful purpose this book can serve. 



Harold A. Wilson. 



BOOKS ON PLANT-PHYSIOLOGY. 



The Physiology of Plants, a Treatise upon the Meta- 

 bolism and Sources of Energy in Plants. By Prof. 

 W. PfefYer. Second fully revised edition. Trans- 

 lated and edited by Dr. Alfred J. Ewart. Vols. i. 

 (pp. xii + 632) and ii. (pp. viii + 296). (Oxford : at the 

 Clarendon Press, 1900 and 1903.) 



Vorlesimgen iiber Pflanzcnphysiologie. By Prof. 

 Ludwig Jost. Pp. xiii-t-695; with 172 illustrations. 

 (Jena : Gustav Fischer, 1904.) Price 13 marks. 



PROF. PFEFFER is to be congratulated on the 

 completion of his great task — the re-writing, 

 in the form of a second edition, of his well known 

 " Pflanzenphysiologie." The present edition, of 

 which the first instalment appeared in 1897, consists 

 NO. iSl I, VOL. 70] 



of what are practically three volumes containing some 

 1600 pages. Of these, the two first volumes are before 

 us in an English translation. 



The book is a unique one, for it is certain that none 

 has ever appeared giving so complete an account of 

 the physiology of plants. It must be remembered, 

 too, that during the past forty years this branch of 

 science has, through the labours of Sachs, Pfeffer, and 

 a crowd of other workers, made great advances, and 

 has developed into a huge mass of inter-related 

 problems, so that the subject-matter is far more ex- 

 tensive than that which any previous writer has had 

 to deal with. To form some notion of the activity 

 of this department of botany, it is sufficient to look 

 at the references which crowd the pages of the book. 



It is perhaps owing to the mass of new matter which 

 had to be incorporated that Pfeffer has somewhat 

 condensed his presentment of general results. This 

 has some disadvantages, inasmuch as the reader misses 

 the give and take of a full discussion. He gets, it is 

 true, the matured judgment of the author, but he gets 

 it condensed to a somewhat dry and cold essence in 

 which the quality of attractiveness is sacrificed. In 

 what forms the main tissue of the book — the detailed 

 consideration of experimental evidence — Pfeffer is at 

 his best, and rules his armies of fact^ with the easy 

 authority of one who is not only deeply learned, but 

 experienced at first hand with every part of his subject. 



The book follows the broad natural division of the 

 subject into " Stoffwechsel " and " Kraftwechsel," 

 that is, into one volume on metabolism — roughly 

 speaking, nutrition — and two volumes on growth, 

 movement and development. The most notable new 

 feature in vol. ii. of the English edition is the 

 prominence given to " causes of specific shape "; this 

 change is the natural outcome of the recent increase 

 of interest in this field of work, for instance in the 

 researches of Vochting, Goebel, Klebs, Driesch, &c. 

 In consequence of the greater space given to this de- 

 partment (in itself a decided improvement in the new 

 edition), the attention given to the special physiology 

 of growth is relatively diminished as compared with 

 the old edition. The volume also contains short dis- 

 cussions on heredity, variation, and allied questions. 

 It is useful to know the author's views on questions 

 of fundamental importance, but apart from this con- 

 sideration we doubt whether these sections are quite 

 worth giving in a book of this character, since 

 it is impossible for the author to give space 

 for an amount of discussion such as the problems 

 demand. However this may be, and such points are 

 largely a matter of individual opinion, on the main 

 point there can be no doubt ; no one can question the 

 value of such a mass of information grouped in logical 

 sequence, connected by the thoughts and criticisms 

 of the leading plant-physiologist of the present day, 

 and representing the mature result of a long life of 

 strenuous and successful work. 



Dr. Ewart, who has made the English translation, 

 is well qualified for the work, being an accomplished 

 physiologist, and his occasional remarks added in the 

 capacity of editor are of value. The task of trans- 

 lating German requires a certain courage as well as 



