DISCOVERY 



165 



in a limited time, must necessarily put more of himself 

 into his lecture than he would if he were merely expanding 

 liis ideas in the quiet of his study. For a lecture he 

 must choose the right facts and ideas germane to his 

 theme very carefully, describe things clearly, omit 

 cumbersome details, avoid side-issues, and make the 

 whole as plain and interesting as possible. These are 

 precisely what the general reader likes a writer to do. 



Dr. Jean's Halley Lecture is a case in point. It is an 

 excellent example of semi-popular exposition. He gives 

 an account of Laplace's nebular hypothesis, shows that 

 it will not explain, as Laplace hoped it might do, the 

 origin of our solar system, but that with a little modifica- 

 tion it explains very satisfactorily the birth of stars from 

 a nebula of hot rotating gas. Much of the lecture is 

 concerned with this point. In the second part the 

 lecturer discusses the formation of our solar system. 

 Planets, he shows, are not evolved from a star as the 

 star has evolved from a nebula. They are probably 

 produced as the result of one star passing in its course 

 sufficiently near to another permanently to affect it. 

 Calculation shows that violent disturbance of this kind 

 will be the lot of very few. In consequence systems such 

 as the solar system " must be rare in the sky . they may 

 be normal in the sense that the events which formed the 

 planets out of our sun might have happened to any star ; 

 but they are abnormal in the sense that such events 

 have in all probability happened only to very few. 

 Indeed, it is just within the bounds of possibility, although 

 quite, I think, outside the bounds of probability, that our 

 systern is unique — that out of the two or three thousand 

 million stars which people space, our sun may be the only- 

 one attended by satellites. To carry this train of thought 

 one step farther, it is just possible, although again quite 

 improbable, that our earth may be the only body in the 

 whole universe which is capable of supporting life." 



That is surely a highly interesting statement from 

 modern science. And later Dr. Jeans expresses this 

 thought in a different way. " We begin to suspect that 

 life is not the normal accompaniment of a sun, since 

 planets capable of sustaining life are not the normal 

 accompaniment of suns. Astronomy . . . begins to 

 whisper that [life] must necessarily be somewhat rare. 

 Her suggestions, although still vague, seem to indicate 

 that our terrestrial life forms a greater proportion of the 

 sum total of all the life of the universe than we at one 

 time thought." 



Botany of the Livnig Plant. By Prof. Bower, Sc.D., 

 F.R.S. Second Edition. (Macmillan & Co., 25s. net.) 



Professor Bower's textbook, " framed on the lines of 

 the annual course of Elementary Lectures on Botany 

 given in Glasgow University for more than twenty years," 

 was first published in 1919. The author is recognised as 

 one of the leading authorities on that branch of Botany 

 which is more especially concerned with the form and 

 structure of plants ; by his intensive study of the ferns 

 and allied plants he has done more than any of his con- 

 temporaries to provide trustworthy data which throw light 

 on the relationships of certain families and on their relative 



position in the order of evolution. In his book, as one 

 would expect, he has given an attractive picture of the 

 plant kingdom from the standpoint of a botanist who 

 thinks of a plant as a complex machine fitted by its 

 structure for the manifold activities of a living organism. 

 In the first edition it was thought by some reviewers that 

 too little attention had been paid to the cell as the unit 

 of plant structure. The living protoplasm of the cells 

 is the seat of the innumerable chemical-physical pheno- 

 mena which form the basis of life, and it is of the utmost 

 importance that students should realise at an early stage 

 in their career that a knowledge of the properties of the 

 cell-contents is the first step towards an intelligent appre- 

 ciation of the mechanism of plant life. The addition of 

 a chapter on the living cell has added considerably to 

 the value of the book. Other alterations are also im- 

 provements. The addition of a chapter on Evolution, 

 Homology, and other subjects of fundamental importance 

 draws attention to conceptions which are liable to be 

 neglected in a book primarily concerned with supplying 

 the raw material of botanical facts. It is clearly im- 

 possible, even within the limits of a bulky volume, to deal 

 thoroughly with the diflerent divisions of the plant- 

 kingdom from the dual point of view of structure and 

 function. Every teacher knows that one of his greatest 

 difficulties is to decide what to omit. A course on 

 elementary botany is merely an introduction ; the aim 

 should be to illustrate fundamental principles, to enable a 

 student to grasp essentials, and to awaken his interest in 

 plants as living things. Professor Bower's treatment of 

 the subject is both scholarly and interesting ; he is careful 

 of detail and does not lose sight of its application to the 

 major problems with which the biologist is concerned. 

 In a general textbook for elementary students it is 

 perhaps superfluous to include an account of many fami- 

 lies of flowering plants, as the author has done in Appendix 

 A. The important point is to give a student a general 

 idea of the nature of a flower, to enable him to appreciate 

 the range of floral structure within a family, and so to 

 understand the meaning of a natural system of classifica- 

 tion, and to teach him how to use a Flora in order that he 

 may identify plants in the field. The more detailed 

 systematic treatment of families of flowering plants is 

 provided for in various books devoted to that branch of 

 botany. A. C. S. 



A Perthshire Naturalist : Charles Macintosh of Inver. 

 By Henry Coaxes, F.S.A. Scot. Foreword by 

 Prof. J. Arthur Thomson and Prof. Patrick 

 Geddes. (T. Fisher Unwin, Ltd., i8s.) 



Mr. Coates describes the life-story of a poor but very 

 remarkable Scotsman — rural postman, naturalist, and 

 musician — who died at the age of eighty-two at the 

 beginning of last year. Macintosh was the first-born of 

 a hand-loom weaver — one of the kind you read about in 

 Barrie's Window in Thrums. He tried saw-milling on 

 leaving school, but an accident that maimed his left 

 hand when he was nineteen led him to become a postman. 

 His beat lay in the particularly charming countryside 

 around his native village, Inver, a tiny place across the 



