January 26, 1893] 



NATURE 



291 



shown is not surprising. It is due to the too free use of 

 metaphorical language on the part of expounders of the 

 Darwinian hypothesis. 



In the chapter entitled " Criticisms of the Theory of 

 Natural Selection," an interesting digest is given of the 

 work of Prof. Ewart and others on the electric organ 

 of the skate, concerning which Mr. Romanes says, "I 

 freely confess that the difficulty presented by this case 

 appears to me of a magnitude and importance altogether 

 unequalled by that of any other single case— or any 

 series of cases — which have hitherto been encountered 

 by the theory of natural selection." And he adds, " So 

 that, if there were many other cases of the like kind to 

 be met with in nature, I should myself at once allow that 

 the theory of natural selection would have to be dis- 

 carded," by which he means, we presume, that the theory 

 would have to be discarded as offering a solution of such 

 cases. 



The book contains many excellent illustrations, the 

 series which show the variations due to artificial selec- 

 tion being a noteworthy feature. They, and the volume 

 which contains them, will prove of service to those 

 general readers for whom, as the author tells us in his 

 preface, this exposition of the Darwinian theory has 

 been mainly prepared. 



FERNS OF SOUTH AFRICA. 

 The Ferns of South Africa, containing Descriptions and 

 Figures of the Ferns and Fern-allies of South Africa. 

 By Thomas R. Sim. 275 pp., 159 plates. (Cape Town 

 and Johannesberg : J. C. Juta and Co. London : Wm. 

 Wesley and Son, 1892.) 



THE present work will be a useful and acceptable addi- 

 tion to ourstock of fern-books. It contains descriptions 

 and plates of all the ferns and fern-allies known to exist in 

 Africa south of the tropic of Capricorn, the same area 

 which is included by Harvey and Sender in their " Flora 

 Capensis," three volumes of which, including the orders 

 from Ranunculaceas to Campanulaceas, have been pub- 

 lished. The author won the Jubilee gold medal given by 

 the North of Scotland Horticultural Association, and for 

 many years has filled the post of curator of the Botanic 

 Gardens at King William's Town. Several years ago 

 Mr. Sim published an illustrated handbook of the ferns 

 of Kaffraria, and now he has extended his area so as to 

 include the whole of South Temperate Africa. 



The fern flora of the Cape does not show the same 

 richness and remarkable individuality which characterises 

 its phanerogamic flora. It is probable that the flowering 

 plants of this area are not less than ten thousand, and the 

 number of large endemic genera and of species is very 

 considerable. In ferns we get in South Africa 179 

 species, out of which 42 species, or something under 

 25 per cent., are endemic. There is no genus 

 that is peculiar to the Cape ; of Mohria, which 

 comes nearest, the Cape sf>ecies, M. caffrorum extends 

 to Madagascar and Tropical Africa, and two new species 

 have lately been found in the high regions north of the 

 colony. The section Rhizoglossum of the genus Ophio- 

 glossum, which differs from the true adder's tongues by 

 having the fertile spike separate from the barren frond, 

 the single species, O. bergianum, is peculiar to the Cape. 

 NO. 1213, VOL. 47] 



Hymenophyllum is represented by 8 species, Tricho- 

 manes by 5, Adiantum by 6, Cheilanthes by 8, 

 Pellaea by 14, Pteris by 7, Lomaria by 5, Asplenium 

 by 25, Nephrodium by 12, Polypodium by 12, 

 Acrostichum by 8 ; and Lycopodium by 8 species. 

 Some of the species, e.g. Vittaria lineatia, Marattia and 

 the two tree-ferns, are tropical types ; some, such as 

 Cystopteris fragilis and Lycopodium clavatutn, are com- 

 mon to Britain and the Cape. Todeabarbaraxs confined 

 to the Cape and Australia, and abundant in both areas. 

 Lomaria alpina is a plant of all the three south-temperate 

 areas. Blechnum australe of the Cape is not, I think, 

 really distinct specifically from B. hastatum, and is widely 

 spread in South Temperate America. 



Lomaria punclulata is remarkable for its polymorphic 

 fructification, which is sometimes like that of a Scolo- 

 pendrium. Asplenium lunulatum is remarkable for its 

 variability in outline and cutting. 



Mr. Sim gives introductory chapters on the parts of 

 ferns and their nomenclature, on their reproduction and 

 propagation, on their cultivation and the preparation of 

 herbarium specimens, and on the history of the discovery 

 of the Caf>e species and the books and papers that have 

 been written about them. His statistic table on page 34 

 needs much revision in some of its items. He gives the 

 ferns of Madagascar at 144. The number now known in 

 the island is 326 true ferns and 40 fern allies, a total of 

 366. There are nothing like 683 species and 458 endemic 

 types in Africa and its islands. When I counted them 

 up in 1868 I made the two figures 346 and J 27. Since 

 that date probably 100 species have been added. Mada- 

 gascar, Bourbon, and Mauritius are very rich in ferns, 

 but Continental Africa is very poor both in number of 

 species and in peculiar types as compared with Asia and 

 America. 



The descriptions are carefully drawn up from the study 

 of actual specimens, and by the aid of these and the 

 plates there can be no difficulty for any one, even without 

 any previous botanical knowledge, in making out the name 

 of any reasonably complete specimen of any of the Cape 

 species. 



Therefore, no doubt, the existence of such a book will 

 give a great impulse to the study of ferns by ladies and 

 others who reside in or visit the Colony. 



J. G. Baker. 



OUR BOOK SHELF. 



Newcomb-Engelmann^s Populdre Astronomie, Ziveite 

 vermehrte Auflage. Herausgegeben von Dr. H. C. 

 Vogel. (Leipzig : Wilhelm Engelmann, 1892.) 

 The well-known Popular Astronomy of Prof. Newcomb 

 was translated into German by Rudolf Engelmann, and 

 published in 1881 with considerable additions and alter- 

 ations, most of which were improvements. It was very 

 favourably received on its first appearance in German, 

 probably because it is not only comprehensive, exact, and 

 scientific, but has a fresh and vigorous style, in pleasing 

 contrast to the ponderous German standard works. The 

 original translator being dead, the publishers entrusted 

 the work of preparing a new edition to Dr. H. C. Vogel, 

 Director of the Astrophysical Observatory at Potsdam, a 

 task for which he was specially fitted, because astronomical 

 progress during the decade since the appearance of the 

 first edition of the book has been mainly in his special 



