August 4, 1910] 



NATURE 



137 



text-book from those in common use already. We 

 note the usual unfortunate preference for the equation 

 y = n!.v+c to represent a straight line, instead of the 

 homogeneous form ?.x-|-jny + H=o. As a natural con- 

 sequence, we find the equations y = mx-^ V(a^m' + 6'), 

 y = mx'ralm, for the tangents to an ellipse and 

 parabola respectively ; and we are still left to wonder 

 why no teacher has the courage to write an elemen- 

 tary text-book which uses the tangential equations 

 <i-/- + b'»i- = »^, In— am- = 0. 



The chief innovation consists in a short chapter 

 (xii., pp. J41-57) on higher plane curves, such as the 

 cissoid, conchoid, lemniscate, cycloid, and some of 

 the simpler polar curves; but as no Calculus is used, 

 nearly all their more interesting properties have to be 

 omitted, and it seems doubtful if the mere tracing of 

 the curves is of sufificient interest to justify their intro- 

 duction here. We should have preferred to see this 

 space devoted to an extension of the chapters on solid 

 geometry, which occupy only 30 pages, and are too 

 brief to be of much service to beginners. 



T. J. V\. B. 



SC HUGH'S MANUAL OF FORESTRY. 

 Schlich's Manual oj Forestry. Vol. ii. : Silviculture. 

 By Sir \Vm. Schlich, K.C.I.E., F.R.S. Fourth 

 edition, revised. Pp. ix + 424. (London : Bradbury, 

 .\gnew and Co., Ltd., igio.) 



THIS book is a decided advance on the first edition 

 of Schlich's "Silviculture," and a considerable 

 amount of new matter has been added. 



Probably the original intention of Schlich's 

 ■■ .Manual " was to provide a text-book on the general 

 jirinciples of forestry adapted to the needs of Indian 

 and Colonial forest officers. While this object is still 

 met, the author has evidently made an effort (and we 

 think successfully) to adapt the work better to British 

 needs than was the case in earlier editions. 



To accomplish this successfully is not perhaps the 

 easy task many might imagine. It is true the prin- 

 ciples of forestry are the same over all, but details 

 in practice must of necessity vary, and climatic differ- 

 ences also tend to modify the relative silvicultural 

 value of various species of trees for any country, or 

 even for districts of a country. 



The book is divided into four parts : part i. deals 

 with what the author designates "The Foundations 

 of Silviculture." Here we have a full discussion of 

 such matters as climate, soils, effects of forest vege- 

 tation on locality ; development of forest trees ; char- 

 acter and composition of woods ; advantages and dis- 

 advantages of mi.xed woods ; and rules for forming 

 pure and mixed woods. The various silvicultural 

 systems are also described in detail. 



Part ii. is concerning the " Formation and Re- 

 generation of Woods." Fencing, soil preparation, 

 sowing, planting, and tree nursing management are 

 fully treated. L'nder . this head also the various 

 modern methods of natural regeneration are described. 



Part iii. deals with the tending of woods through- 

 out the various stages, from early youth to maturitv. 



Of part iv. ninety pages are devoted to 

 NO. 2127, VOL. 84] 



a brief discussion of the silvi(^ultural characters 

 of British forest trees. lender the convenient title 

 of " British Forest Trees " the author includes 

 several recently introduced species, some of which are 

 certainly of doubtful utility for British conditions, as, 

 e.g., American Black Walnut and Black Cherry. He 

 wisely refrains, however, from definitely recommend- 

 ing such species for general planting. 



The book is well illustrated. Although some of tlie 

 illustrations are necessarily diagrammatic in character, 

 they are none the less valuable to students on that 

 account. 



Schlich's "Silviculture" continues to hold its own 

 as one of the chief standard works on the subject, and 

 should be in the hands of all students of forestrv. 



J. F. A. 



GENERAL BIOLOGY. 

 General Biology: a Book of Outlines anti Practical 

 Studies for the General Student. Bv Prof. James C>. 

 Needham. Pp. xiv + 542. (Ithaca, N.Y. : The 

 Comstock Publishing Co., 19 10.) Price 2 dollars. 



WE have long felt that if biology is ever to lake 

 the place which it undoubtedly should in our 

 educational system, there will have to be some radical 

 reform in the manner in which it is taught, or perha[)S 

 it would be more correct to say in the selection of 

 those portions of the subject which are to be taught. 

 The type-system, excellent as it is in many respects, 

 has had far too much influence on biological curricula, 

 and the over-specialisation in zoology and botany has 

 resulted in a general neglect of those general prin- 

 ciples which are the life-blood of both. Fortunately, 

 signs are not wanting of a widespread striving to- 

 wards a more rational treatment of the subject, and 

 in this respect the Americans appear to be taking the 

 lead. The work before us, modestly described by its 

 author as "A Book of Outlines and Practical Studies 

 for the General Student," strikes us as being delight- 

 fully refreshing and original. Its scope is, perhaps, 

 almost too comprehensive. There are only seven 

 chapters, but they are very long ones. In the first, 

 the interdependence of organisms is illustrated by 

 the relations between flowers and insects; galls, and 

 the relation between ants and a[)hids. The second 

 deals with the simpler organisms, illustrated by typical 

 alga and protozoa. The third is devoted to organic 

 evolution, with a brief account of the animal and 

 vegetable series and the general principles of the 

 subject. The fourth discusses inheritance ; the fifth 

 the life-cycle; the sixth the adjustment of organisms 

 lo environment; and the seventh the responsive life of 

 organisms. 



A leading feature of the book is a set of practical 

 exercises at the end of each chapter. These are extra- 

 ordinarily varied and interesting, and well calculated 

 to impart a real vitality to the subject, though perhaps 

 some of them, such as the observations on the internal 

 metamorphosis of insects, are rather too specialised. 



The illustrations are excellent and to a large extent 

 novel, and the portraits of Schultze, Pasteur, Von 

 Baer, I innaeus, Agassiz, Darwin, Leeuwenhoek, 



