August 25, 1910] 



NATURE 



''-li 



regarding the limiting position of the centre of pres- 

 sure for vanishing inclination, and the probable influ- 

 ence of skin friction, careful examination of the con- 

 ditions of experiment seems desirable. 



We have before us a prospectus, issued last April, 

 of "Aviation Investment and Research, Limited," 

 promoted with a share capital of ;^ioo,ooo, with 

 Major J. A. Meldon and Mr. Ernest Dawe, 33 South- 

 ampton Street, as secretaries, a venture the progress 

 of which will be watched with considerable interest. 



If there is one inference to be drawn from a survey 

 of the papers,, mentioned in this review, it is that a 

 large amount of attention has been given to the 

 application of the statical formulas, X = Rcosa, 

 Y = Rsina, to problems of lift and drift, but that the 

 other equations of equilibrium or of motion of a 

 solid body have been until now largely left to chance, 

 the skill of the aviator being made to take the place 

 of exact mathematical calculation, with uncertain re- 

 sults. It may be safely stated, however, that the time 

 is not very distant when "equilibrium and stability of 

 aeroplanes " will become a subject suitable for courses 

 of lectures in the mathematical departments of our 

 universities. G. H. Bryan. 



ECONOMIC MYCOLOGY. 

 Fungous Diseases of Plants; with Chapters on 

 Physiology, Culture Methods, and Technique. By 

 Prof. B. M. Duggar. Pp. xii + 508. (London: 

 Ginn and Co., n.d.) Price 8,s. 6d. 



PROF. DUGGAR 'S book, although intended 

 primarily for the student in the United States, 

 will be welcomed by the plant pathologist in all 

 countries. 



The plan on which the book is arranged is excel- 

 lent, and the subject-matter is illustrated with 240 

 drawings and photographs, which are almost all 

 good, while some of the photographs of diseased 

 plants (especiallv those taken by Prof. H. H. Whetzel) 

 stand out with an excellence which could not be 

 surpassed. In the first fifty pages a full and lucid 

 account is given of isolation and pure-culture methods 

 and the technique of fixing, imbedding, and staining; 

 this is followed bv chapters on various physiological 

 phenomena, such as the requirements of fungus spores 

 for germination, aspects of parasitism and sapro- 

 phytism, and so forth, concluding with a valuable 

 chapter on environmental factors. A short chapter 

 deals with the " principles of disease control," includ- 

 ing the preparation of fungicides. This chapter might 

 with advantage have been amplified, and information 

 given on such points as the strength of Bordeaux 

 mixture to be used in potato spraying, the nature of 

 the spray required in the various washes, and the 

 main types of spraying machinery. The information 

 given concerning the lime-sulphur wash is too scanty 

 to be of much practical value. With regard to the 

 fungicidal action of Bordeaux mixture, the statement is 

 made : — 



" It has been fairlv well demonstrated that the ger- 

 minating spore will absorb from the nearly insoluble 

 NO. 2130, VOL. 84] 



copper compounds of Bordeau.x mixture sufficient toxic 

 substances to cause its death." 



No account is given of the legislative control of 

 plant diseases, an omission which should be rectified 

 in any future edition. .America was the first country 

 to take State action in this direction, and many inter- 

 State regulations controlling the spread of diseases 

 are now in force. At the present time the Govern- 

 ment of the United States is considering the best 

 means of puttinc into force an- Act to secure the 

 examination of all plants at the ports of entry in order 

 to prevent the importation of fungus and insect pests. 



The remaining part of the book, consisting of 400 

 pages, describes the various species of fungi and 

 bacteria which are known to cause injury to plants of 

 economic importance in America. The aim of the 

 author has been, in the treatment of each disease, to 

 keep in view three considerations — (i) to describe the 

 pathological effects and other relations of host and 

 parasite; (2) to make clear the life-history of the 

 organism causing the disease ; and (3) to indicate the 

 methods of prevention and control. A short biblio- 

 graphy, which will be very valuable to the student 

 in other countries besides America, precedes the 

 account of each disease. 



Considering the amount of information which is 

 given on so large a number of diseases, the sugges- 

 tion that some of the more important diseases might 

 have been given a fuller treatment must seem some- 

 what ungracious. It is, however, unsatisfactory for a 

 student to be merely told, e.g. concerning Botrytis 

 cinerea, that " much interesting biological work has 

 been done upon this fungus." The bare statement that 

 follows, viz., "infection frequently fails when conidia 

 germinate directly upon the surface of delicate parts," 

 is likely to be somewhat misleading, since it is not 

 qualified by any reference to the results obtained by 

 Kissling (whose name is quoted in the bibliography), 

 which demonstrated that certain plants can be easily 

 infected in this way. One or two omissions in the 

 list of diseases may be noticed. The mildew 

 {Sphaerotheca humuli) which attacks the hop and 

 other plants (but not the rose) in Europe is in the 

 United States commonly found attacking the leaves 

 of roses ; no mention is made of this disease, the 

 "mildew" of the rose being attributed entirely to S. 

 pannosa, which, in the States, is apparently the less 

 common of the two species. It is curious to find no 

 reference to the "mildew" of the cultivated hop. 

 Another omission is the " covered smut " of barley 

 (Vstilago hordei), which is not uncommon in the 

 States. The "crown gall" of lucerne (Urophhctis 

 alfalfae) is found, not only "in South America and 

 Germany," but is known also in Switzerland and 

 Italy, and has occurred in England in Kent. 



Except for a few comparatively unimportant omis- 

 sions, however, this manual is thoroughly comprehen- 

 sive. Throughout the work there is evidence of much 

 first-hand knowledge of the diseases described. In 

 some cases Prof. Duggar has followed up his re- 

 searches in the States by paying a visit to Europe to 

 studv the same disease there, and in this way he has 

 been able to throw light on certain vexed questions of 



