NATURE 



121 



THURSDAY, JUNE lo, 1897. 



PLANT PATHOLOGY. 

 Diseases of Plants induced by Cryptogamic Parasites. 

 By Dr. Karl Freiherr von Tubeuf. English Edition, 

 by William G. Smith, B.Sc, Ph.D. Pp. xv + 598. 

 (London : Longmans, 1897.) 



WHEN the German edition of this work appeared, 

 early in 1894, it at once took rank as one of the 

 most comprehensive and accurate treatises on the subject 

 that had as yet appeared, and the English edition we 

 now have to welcome still deserves this tribute to its 

 merits, for the author has taken the opportunity of adding 

 considerably to the already bulky volume. 



The fungus-diseases of plants now number so many 

 forms, that no apology is necessary for treating them 

 separately from the very numerous other diseases of 

 plants ; but it should be clearly borne in mind that only 

 part of the very wide subject of the pathology of plants 

 comes under this head, as may be readily seen on com- 

 paring the new edition of Frank's " Krankheiten der 

 Pflanzen," which has appeared in the interval, and of 

 which the first volume is devoted to the diseases due to 

 non-living agents, the second to those caused by parasitic 

 plants (not fungi only), and the third to pathological 

 states induced by animals. 



Thus comprehensive works on the whole range of this 

 vast subject are not wanting, and the student should 

 observe that the standpoint from which a treatise like this 

 is written differs considerably from those assumed by 

 writers on the general subject of pathology, or those who 

 deal with the morphology and physiology of the fungi. 



Berkeley, Frank, Sorauer, and Hartighave shown that 

 the diseases of plants constitute a theme by itself which 

 may be treated with reference either to the symptoms 

 and progress of the pathological conditions, where the 

 victim of disease furnishes the principal phenomena dis- 

 cussed, or to the causes or agents which induce these 

 pathological conditions. These agents may be internal or 

 external, and the latter comprise factors of the non-living 

 environment, or living organisms — animals or plants in 

 anti biotic relations to the host, or victim. 



The present large volume, of more than 600 pages with 

 330 illustrations, is devoted, as said, to the narrower 

 theme, and bears witness to the astonishing progress 

 made in the study of the parasitic fungi during the last 

 quarter of a century. 



Its subject-matter is principally the fungi themselves, 

 and in character it partakes of the nature of a flora or 

 diagnostic list, and a treatise on symptoms and thera- 

 peutics, with bibliographical references for those who 

 wish to launch further into this particular arm of the sea 

 of knowledge. It is thus neither a complete treatise on 

 the biology of fungi, nor a detailed work on pathology, 

 but — and in this reside its peculiar characteristics — a 

 volume compiled to meet the wants of an increasing 

 class of students who wish to know something of the 

 parasitic fungi themselves and what plants they attack ; 

 something of the mode of attack and the symptoms 

 induced ; and something of the suggestions for combating 

 the diseases which have been supplied by experiments in 

 the field. It is thus a typical example of a class of book 

 NO. 1 44 1, VOL. 56] 



evolved under the stimulus of the practical spirit of the 

 age, and, in fairness to all be it said, of a high standard 

 of excellence as scientific literature ; further, it will be of 

 no use to the crammer, to the examinee, or the dilettante, 

 but must take its place on the shelf of the serious worker, 

 the true naturalist, and the educated cultivator of plants 

 as an indispensable work of reference. 



The book consists of two parts, of which the first con- 

 tains chapters on the nature of parasites and parasitism, 

 the reactions between host and parasite, infection, pre- 

 disposition, preventive measures, and the economic im- 

 portance of the diseases of plants, together with a short 

 summary of the facts of symbiosis. 



The second, and far larger part, is devoted to a 

 systematic account of cryptogamic parasites — the fungi 

 proper, slime-fungi, bacteria and pathogenic algas being 

 included. The system followed is that of Brefeld, the 

 saprophytic forms being omitted. 



Objection may be made to the inclusion of the algas 

 and symbiotic forms, such as mycorhiza, the organisms 

 of the leguminous nodules, lichens, &c.; but Tubeuf has 

 something of his own to say about these matters, and 

 although I do not agree with his strained attempts to 

 classify the phenomena of saprophytism, parasitism, and 

 symbiosis, and regard his selection and definition of the 

 terms niitricisin and individualism as particularly un- 

 fortunate and misleading, I think that he was quite right 

 in discussing these matters here, if only to help in 

 emphasising the real nature of parasitism by contrast. 



The author has avoided several pitfalls. It would have 

 been easy to give way to temptations to discuss in detail 

 several disputed points, especially as Tubeuf is himself 

 an investigator with strong views of his own ; but it is 

 noticeable throughout that he attempts a fair summary of 

 the published accounts. The fault of over-description 

 has also been wisely and ably avoided, and this, on the 

 whole, without sacrifice of usefulness ; though it must be 

 borne in mind that a good deal of preliminary acquaint- 

 ance with the subject is necessarily demanded from the 

 reader. Again, there is sufficient treatment of theoretical 

 matters to make the book attractive to botanists not 

 specially concerned with pathology in detail, and, further, 

 the hints on practical therapeutics, though necessarily 

 short, appeal to the cultivator himself, and show that the 

 book is designed to help him. 



One fault of omission must be mentioned, if only in 

 justice to those who have done good work in this country : 

 the English literature is almost wholly ignored. We 

 hesitate whether to blame the author — who only follows 

 the too common practice of continental writers — or the 

 editor for this. In any case the latter might have in- 

 cluded references to Massee's and Somerville's experi- 

 ments with Plasmodiophora, in his notes, to say nothing 

 of other work by English botanists. 



A feature in the work, which adds immensely to its 

 value, is the selection of photographic illustrations of the 

 diseased plants themselves, showing how the victims of 

 fungus attacks look. This is as near an approach to taking 

 the student into the field and showing him the disease at 

 work, as can possibly be made in a book ; and when we 

 reflect that this— so to term it— clinical study is as import- 

 ant for plant diseases as it is in the case of human diseases, 

 its importance is obvious. Few people are aware how 



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