November i6, 191 i] 



NATURE 



75 



i Association, this selection is very welcome, and the 



I book itself, at its modest price, is distinctly suggestive 



' to the teacher. The illustrations, even when most 



effective, are rarely chosen from hackneyed subjects. 



; VVe can scarcely do better than Stare Cove, Lulworth, 



jor the Giant's Causeway, which naturally appear; but 



i we can now avail ourselves of the limestone pinnacle 



!of Pickering' Tor, of eight views of the River Artro, 



near Harlech, from its source among the boulders to 



the sea, and of the Severn Valley in the Triassic plain 



I of Worcestershire. Broad landscapes like the last have 



j loo often been neglected. Miss Sharpe gives us also 



the Silurian escarpments near Malvern, the rounded 



j forms of the Longmynd, and the ice-worn gneissic 



I floor of Sutherland. Details like an erratic near 



(Harlech and pot-holes on the Gelt have also obvious 



(uses. The subject may easily be extended into future 



jvolumes, if the enterprise meets with the success that 



jit deserves. 



I A neat coloured geological map of the British Isles 

 lis given, but no useful purpose appears to be served 

 by the insertion of tables of rock-forming minerals 

 or of the classification of rocks, which cannot be 

 regarded as either adequate or appropriate. The 

 statements, moreover, made in this brief form are not 

 always accurate. Opal is only partially described as 

 " hydrated silica, brilliantly coloured." The term 

 "glassy" applied to sanidine ought to have been long 

 ago abandoned. "Carbonate of calcium" does not 

 necessarily crystallise in rhombohedral crystals, since 

 two forms are described below, one of which, 

 ragonite, is here said to be triclinic. In the elassifi- 

 ation of the stratified rocks, "silica" and "silicates 

 f alumina " are treated as minerals. These matters 

 ip"ht be left with the text-books, to which the pre- 

 face so properly refers. 



Die Ansucht Tropischer Orchideen aus Samen. Neue 

 Methoden auf der Grundlage des symbiotischen Ver- 

 hdltnisses von Pjlatize und Wurzelpilz. By Dr. H, 

 BurgefT. Pp. iv + 90. (Jena : Gustav Fischer, 191 1.) 

 Price 3.50 marks. 



It was announced by the French botanist, Noel 

 Bernard, in 1904 that a symbiotic fungus inhabits the 

 roots of many orchids, and that continued germina- 

 tion of the seed of such orchids is dependent upon 

 the entrance of the fungus mycelium to renew the 

 symbiotic union. This conclusion raised further 

 problems, particularly whether the fungus differs in 

 different orchids and how it may be isolated and 

 inoculated. These are the practical points treated by 

 pr. Burgeff, who provides full instructions for raising 

 (seedlings in accordance with rigidly scientific prin- 

 |:iples. The methods are laborious. It is necessary to 

 jTiakc pure cultures of the fungus, obtain aseptic seeds, 

 ^jningle the two symbionts, grow them artificially, and 

 • ransfer finally the young i)lant to natural conditions, 

 jrhe author also cultivated a number of mycelia taken 

 jTom differen.t plants with the view of distinguishing 

 'iilTerent varieties or species of fungus; the ijeneral 

 result is indicated in a diagram showing that the 

 .Tiycelium of a given culture may serve for one, two, 

 |)r rarely for more genera. Having thus shown how 

 pure cultures should be made and described many 



fxperiments that he successfully carried out on these 

 ines, he indicates a less troublesome method which 

 onsists in sowing the seed on'sterilised fungus-infected 

 toil. 



It is unlikely that professional orchid gfrowers will 

 dopt either of the methods described, because it is 

 'n most cases an easy matter to raise seedlings under 

 ordinary conditions by adding portions of the old roots 

 •j>r even soil from old cultures to the compost in the 

 eed-pan. Nevertheless, the researches of Dr. Burgeff 



;i NO. 2194, VOL. 88] 



are theoretically and practically of great value, and 

 should be carefully noted by growers, as they may 

 serve to explain unexpected failures. 



Elementary Applied Mechanics. By Prof. A. Morley 

 and W. Inchley. Pp. viii + 382. (London: Long- 

 mans, Green and Co., 191 1.) Price 35. net. 

 This book is intended for beginners of limited mathe- 

 matical attainments, and, to meet the needs of such, 

 extensive use is made of graphical methods and of 

 numerical illustrations. Many worked-out exercises 

 are included, together with others intended for solu- 

 tion by the student. Simple laboratory experiments 

 are described. The standard is that of Stage I. of 

 the Board of Education, and the method of treatment 

 is quite orthodox. An introductory chapter on men- 

 suration and measuring appliances is followed by 

 chapters on elementary statical principles, leading up 

 to the consideration of simple frames. Work, fric- 

 tion, and machines are then considered. Five very 

 good chapters on the strength and elastic properties of 

 materials are included, and the elementary laws of 

 hydraulics form the subject-matter of the last three 

 chapters. 



The illustrations are clearly drawn, and are mostly 

 correct. An exception occurs on p. 115, where a Prony 

 brake is illustrated, having two mistakes in its .design. 

 In the chapters dealing with the composition and 

 resolution of forces, it would have been better to 

 omit the arrows shown on the triangles and 

 polygons of forces. These cannot be shown on the 

 force diagrams for frames, and a habit of inserting 

 arrows which have to be omitted in subsequent 

 diagrams is easier acquired than dropped by the be- 

 ginner. We also observed several diagrams in which 

 the resultant, found from the force diagram, has not 

 been inserted in its proper place. The principal 

 author is well known from his work on the strength 

 of materials, and the present volume should take a 

 good place among the other elementary text-books on 

 the same subject already in existence. 



The London University Guide and University Corre- 

 spondence College Calendar, 1912. Containing the 

 Regulations for Examinations to be held in 1912 and 

 1913. (London : University Correspondence College.) 

 The private student anxious to graduate at the 

 University of London will find in this volume all the 

 information he needs as to how to proceed. The best 

 plan, in cases where it is possible, is for the student 

 to enter one of the constituent colleges of the Univer- 

 sity and to follow the suitable course of study arranged 

 for intending graduates ; but for young men and 

 women who are compelled to live lar away from a 

 college and whose time is occupied during the day, it 

 would be difficult to find more helpful advice than 

 this book contains. 



Life in the Sea. By James Johnstone. Pp. vii+150. 

 New Zealand. Bv Sir Robert Stout, K.C.M.G., and 

 J. Logan Stout. Pp. viii+185. (Cambridge 

 University Press, 1911.) Price is. net each. 

 Both these volumes belong to "The Cambridge 

 Manuals of Science and Literature," a series which is 

 fast becoming representative of every department of 

 human knowledge. Mr. Johnstone provides a dis- 

 cussion of the general economy of the sea, in which 

 the results of recent investigations of the microscopic 

 life of the ocean are given due prominence. The 

 object of the second book is to show faithfully in a 

 brief wav what New Zealand is and what has been 

 done by her people, the treatment being such as is 

 likelv to appeal to readers who have not seen the 

 Dominion. 



Those " Manuals " arc not of the nature of primers 



