JAN 16 1 



NATURE 



321 



HURS 



OLOGY AND PLANT PATHOLOGY. 

 I Text-book .v and Plant Pathology. 



; . I'rof. J. W. Harshberger. Pp. xiii + 779. 

 (London: J. and A. Churchill, [918.) Price 

 15s. met. 



i^ HIS text-book cannot fail to give much valu- 

 able information to the rapidl) increasing 

 number of students of plant diseases. Part i. 

 deals with mycology in a general sense, compris- 

 sification, morphology, histology, physio- 

 logy, bio-chemistry, md phylogeny. In 

 part ii. general plant pathology is dealt with; 

 the predisposing and determining factors of 

 disease and the botanical phenomena accompany- 

 ing pathologic plant growth are discussed in 

 detail. A very useful chapter, well illustrated and 

 full of practical details, is given on "Practical 

 surgery." Part iii. is entitled "Special 

 Plant Pathology," and comprises a list of the 

 common diseases of economic plants in the United 

 and Canada, followed by a detailed account 

 of about 100 parasitic and non-parasitic diseases, 

 which have been selected either because of the 

 economic importance of the disease over wide 

 ihical areas, or because their study 

 he student tn conned up the practical 

 and the systematic parts of the book. Some 

 very interesting information from various bul- 

 letins of the United States agricultural experiment 

 stations is given in this section. It would 

 have been well if the author had made 

 room for a full account of the wart-disease 

 of the potato (Synchytrium endobioticum), in view 

 of the fact that it is the must destructive disease 

 of the potato known, and that while the United 

 ire believed to be still free, an alarming 

 outbreak occurred in Canada in [912. An account 

 of the methods employed againsl this disease by 

 n-ultural authorities in this country for 

 • ten years would have formed an excel- 

 -li -son for the student of the disastrous 

 results that follow from the neglect of scientific 

 measures in dealing with the early outbreaks of 

 fungous pest. 

 Pari iv. consists of laboratory exercises in the 

 cultural studies of fungi, and this part will endeai 

 the book to the practical working student of 

 igy, in the same wa\ as Percival's "Agri- 

 Botany " has been welcomed by the 

 in agricultural botany. Information is also 

 >n micrometry, microscopic drawing and 

 crography, staining, culture media, and 

 of microtoming. The methods of stain- 

 flagella; of bacteria appear to have been 

 ere, no doubt aci identalrj . 



1 oncludes with appendixes on methods 

 [ miking fungicides .and insecticides tnd their 

 formuke, together with a spraj calendar. The 

 new ammonium sulphide wash might have been 

 mentioned, as this is useful where any dis- 

 coloration of the part of tin plant sprayed (e.g. 

 fruit) is to be avoided. The other appendixes 

 NO. 2^6;. VOL. I02 1 



consist of dichotomous keys to the classification 

 of the Myxogastrales, Mucor, Aspergillus, Peni- 



cillium, the Erysiphaceae, and the Agaricaceae. 



In any future edition it would be well to satisfy 

 the curiosity of the student by giving more in- 

 formation on the subject of Eriksson's "myco- 

 plasm," since it has been advanced to account 

 not only for sudden outbreaks of rusts, but also 

 for the appearance in the spring ol the American 

 gooseberry-mildew. From the remark made by 

 Prof. Harshberger on p. 308 it may be inferred that 

 he belongs to the majority who hold that there is 

 no satisfactory evidence of the existence in Nature 

 of "mycoplasm." The treatment of the subject 

 of specialisation of parasitism seems to us to be 

 too meagre. The subject is not only of great in- 

 terest physiologically, but also of considerable eco- 

 nomic importance. It is a loss to find no account 

 given of the thorough investigations carried out 

 by Marshall Ward in the L'redineae, or of the 

 work of the various mycologists — including 

 G. M. Reed — in the United States on the same 

 problems in the Erysiphaceae. The work recently 

 published by H. YVormald shows that similar 

 phenomena of specialisation occur in the species 

 of Monilia which cause the "brown rot " diseases. 

 Since Prof. Harshberger says that " to be a suc- 

 cessful pathologist one must be a good morpholo- 

 Sfist, histologist, geneticist, and physiologist," 

 some account should have been given the student 

 of the work of Prof. R. H. Biffen, who first 

 established the inheritance of disease-resistance 

 on Mendelian lines. 



The morphological description of the Erysi- 

 phacea; on p. 155 is incorrect, since that family 

 includes one genus with an endophytic mycelium. 

 The common rose-mildew of the United States is 

 not, as stated on p. 461, Sphaerotheca pannosa, 

 but S. humidi. The danger of generalising as to 

 what is the dominant factor in outbreaks of disease 

 under field conditions is shown by Prof. Harsh- 

 berger's statement on p. 324 that "early sowing 

 of winter wheat has been found beneficial in the 

 reduction of the amount of stinking smut, for 

 wheat sown early in October showed no sign of 

 infection, while plants sown at the end of October 

 were much attacked (about 60 per cent.) by the 

 smut." In the case of a field of "bunted " wheat 

 which came under the present writer's notice 

 during- the past season, the percentage of bunted 

 grains, on an actual count, was found to be con- 

 siderably higher in that portion of the field which 

 had been sown a few weeks earlier ! Since 

 "bunt" and "smut" diseases of cereals appear 

 to be on the increase in this country, we may 

 note here the statement, to which Prof. Harsh- 

 berger gives credence, that "in the summer of 

 1914 300 threshing machines were blown up or 

 burned by smut explosions"; the ignition of the 

 oily and dry masses of smut spores is attributed 

 to static electricity in the cylinder of the threshing 

 machine. 



It would be difficult to accept — if this 



sary — all the terms used in this book. While 

 we may have to accept " seciospnre, " "uredinio- 



