January 5, 191 1] 



NATURE 



303 



ISentham and Hooker's " Genera Plantarum," these 

 genera are credited with one and four to five species 

 respectively, and while we might expect some increase 

 in the number of known species since the date of issue 

 of that volume, it is with somewhat of a shock that 

 we find Plat3Stemon credited with fifty-five and Esch- 

 -choltzia with 123 species. In Platystemon forty-nine 



A the species are of Greene and six of Fedde, in 

 Eschscholtzia 104 of Greene and twelve of Fedde. 

 Prof. E. L. Greene, we believe, holds views as to the 



•rigin of species which do not accord with those 

 generally accepted, and these views are no doubt re- 



ponsible for the description of species based on char- 



lCter^ which mij^ht otherwise be regarded as repre- 

 senting mere variants of a single species. Dr. Fedde 

 has not only adopted Dr. Greene's estimate, but added 

 ro the number. He perhaps shrank from the difficult 

 Msk of reducing the species to more workable pro- 



■ortions, and took the path of least resistance. The 

 ■ esult is, however, an increase in the number of those 

 -genera, which, like Crataegus in America, and Rubus 



n the Old \\'orld, have been rendered hopelessly un- 

 Aorkable by any but the most devoted expert. This 

 nethod of treatment of some of the genera leads to 



. want of uniformity in the work as a whole. Thus 

 mder the common poppy, Papaver rhoeas, are twent}- 

 ~ix varieties and subvarieties, which probably have as 

 4ood claim to specific distinction as the '" species " of 

 Platystemon. 



In dealing with the genera of Chelidonieae, Dr. 

 Fedde has followed the limitation of species accepted 

 by Dr. Prain, though he does not adopt his reduction 



•1 several of the genera, Dicranostigma, Hylomecon, 

 and others, to subgeneric rank under Chelidonium. 

 On the whole, however, Dr. Fedde shows a dis- 

 inclination to differ from authority which we do not 

 rxpect from the expert who has exhaustively surveyed 

 the entire field of a large natural order. Thus under 

 Meconopsis, while accepting Dr. Prain 's sections, he 

 suggests with regard to two of these, Aculeatae and 

 Primulinae, that the division is not a natural one. 



As regards the presentation of genera and species, 

 the descriptions are full, the synonymy and geograph- 

 ical distribution are carefully worked out, and collec- 

 tions and numbers are largely cited. The index is a 

 good one, but would be improved by the repetition of 

 the genus name at the head of each column, thus 

 avoiding the necessity for turning back to find the 

 genus to which the species names belong. 



A. B. R. 



OUR BOOK SHELF. 



Woodcraft for Scouts and Others. By O. Jones and 

 M. Woodward. Pp. 156. (London : C. Arthur 

 Pearson, Ltd., 1910.) Price 25. net. 

 That the present generation of country- people do not 

 -tudy woodcraft and field-lore with the zest and 

 thoroughness of their forefathers, is a regrettable fact 

 too well known to all capable of forming an opinion 

 <>n the subject. The nature-knowledge of the old- 

 fashioned shepherd has been replaced by a superficial 

 > ducation of a different class, which is of little or no 

 ■Use to its possessor, and the intimate knowledge of 

 the creatures of the forest, field, and stream owned by 

 ihe professional poachers of a generation ago has to a 



NO. 2149, VOL. 85I 



considerable extent vanished with the diminution in 

 the numbers of that class in many districts. Nor is 

 this all, for ordinary country lads, m some counties at 

 any rate, show a lamentable lack of knowledge of the 

 names of wild plants and birds as compared with their 

 grandfathers. That the scout movement, if properly 

 conducted will do somemmg to improve this state of 

 affairs in the case of the rising generation is almost 

 certain, for it is obvious that to orient one's position 

 in a wood at night, to follow the trail of a suspect, 

 or to escape the attentions of an enemy is impossible 

 without a full knowledge of woodcraft in its widest 

 sense. 



As an aid to knowledge of this nature, the excellent 

 little volume by Messrs. Jones and Woodward is very 

 opportune, if only it reaches the class for which it is 

 primarily intended. Both authors appear to have a 

 thorough grasp of their subject, and the amount of 

 information contained in their work is little less than 

 marvellous. In the tenth chapter there is perhaps a 

 little too much tendency to convert the young scout 

 into a rabbit poacher, and the expression on p. 136, 

 ■' to break the law of trespass," is an indication that 

 the authors are not so well versed in the common law 

 of their own country as they might be. In treating 

 of the animals and plants of the countryside, the 

 authors are just as much at home as when discussing 

 old-fashioned country remedies, or the difference be- 

 tween wholesome and noxious funguses, and their 

 work as a whole leaves little or nothing to desire in 

 the matter of completeness and thoroughness. 



R. L. 



A School Course of Heat. By R. H. Scarlett. Pp. 



xvi + 300. (London : Longmans, Green and Co., 



1910.) Price 3s. 6d. 

 This book is intended for the use of students who 

 have already passed through an elementary course in 

 general physics. The author devotes the first thirty 

 pages of the present volume to a recapitulation of the 

 elementary portions of heat. The rest of the book 

 deals with the more advanced parts of the subject 

 and touches briefly upon some points which do not 

 usually find a place in a school text-book. 



The subject is developed throughout along the line 

 of practical work in the laboratory, but we do not 

 think the laboraton,- experiments are always well 

 chosen. In dealing with the errors of mercury ther- 

 mometers on p. 18, the author states that mercury is 

 not quite uniform in its expansion, and near 50° C. 

 on the scale, there will be a constant error amounting 

 to almost a degree. This error, of course, will depend 

 upon the glass, but one-tenth of a degree is nearer 

 the average correction necessary from this cause. The 

 method employed on p. 62 to obtain the relation be- 

 tween the density of a liquid at different temperatures 

 and its coefficient of expansion will present difficulty 

 to an elementary student, and it is certainly not 

 sufficiently accurate for all experiments as performed 

 in the laboratory. Thus, in the example given on 

 pp. 64, 65. there is an error of 3 per cent, in the 

 calculated coefficient due to the use of this approxi- 

 mate formula. 



Similarly, in the treatment of coefficient of. absolute 

 expansion on p. 70, it is not made clear to the reader 

 which column length is involved in the denominator 

 of the expression obtained. The wrong one is 

 measured in the illustrative example, making a I5 

 per cent, error in the result. The hydrostatic method 

 is a most unsuitable one to employ for the expansion 

 coefficient of ether between 10° and 30°, as given on 

 p. 66. On p. 191 we are told that the steam and 

 hoarfrost lines intersect at 0° C. The chapter on 

 thermal conductivity would have been improved by 



