September 17, 1896] 



NA TURE 



459 



approached it from the point of view which, thanks 

 largely to the often decried "laboratory system," we 

 are enabled to do at the present time. In fact, until 

 botanists had given up restricting their attention to 

 species, and to the grosser external characters of plants, it 

 was not possible for them to apprehend how intimately 

 the welfare, and consequently the distribution, of the 

 organism and of the species is bound up with minute and 

 often apparently trivial details of structure. It is true 

 that the general characters of what we may term the 

 Habitus of groups of plants had been more or less clearly 

 defined. Humboldt and Grisebach had already distin- 

 guished numerous dominant types, and had indicated 

 the general nature of their relationships. 



But what we want to find out is the causal nexus which 

 e.\ists between the plant, and the locality or conditions in 

 which it lives. It is this, the biological, aspect of the 

 question which is the important one for to-day. We are 

 deeply conscious that life is a struggle between conflicting 

 organisms more or less adapted to the conditions of life 

 to which they are e.\posed. We know, too, that in this 

 struggle, no factor is without its due weight in deter- 

 mining the final result. But we cannot hope to unravel 

 the tangle of reasons which may account for the presence 

 of this type here and its absence there, nor can we 

 appreciate the nice adjustment between the individual 

 constituents which compose the type, until we are in a 

 position to investigate the inter-relations existing between 

 the adaptation and the environment to which it responds. 

 Before this could be, it was first necessary to obtain an 

 insight, not only into the minute details of anatomy, 

 but also into their connection with the functions dis- 

 charged by the organism as a whole. Only then can we 

 appreciate the true meaning of the peculiarities presented 

 by members of such characteristic floras as alpines, 

 epiphytes, mangrove swamps, and the like. 



It is not that the problems of distribution have hitherto 

 attracted but little interest — far from it — but that before 

 they could be successfully grappled with, a laboratory 

 training formed an indispensable preliminary. But it is 

 only a preliminary. It is all very well to study collections 

 of plants, whether in the form of pickled material, or 

 herbarium specimens, or even as living beings in hot- 

 houses. It is only by travelling, and seeing the things 

 as they actually grow under natural conditions, that one 

 is in a position to estimate the importance of this or 

 that structure, and its relation to the welfare or existence 

 of the species. It may not be necessary to travel far 

 in order to make some progress in this study. Our own 

 country affords abundant opportunity to those who know 

 how to use their eyes ; still, there can be no question but 

 that it is in tropical regions that the purposefulness of 

 structural modifications most forcibly obtrudes itself on 

 the mind of the observer. 



The questions involved are most fascinating, and they 

 are most intricate. Hence it is the more important that 

 we should address our inquiries in an orderly manner if 

 we are to successfully analyse and classify the numerous 

 factors concerned. To indicate how this may be done 

 is one of the objects of Prof Warming's book, and he 

 may fairly claim to have largely succeeded in his efforts. 



He discusses, in the first place, the general effect of 

 physical conditions on plant-life ; and his remarks are 

 NO. 1403, VOL. 54] 



always interesting, even where we do not quite agree 

 with the conclusions to which he arrives. He then gives 

 a short classification of the different characteristic groups 

 of plants, which he assembles in four different divisions 

 —the Hydrophytes, Xerophytes, Halophytes and Meso- 

 phytes, the last including what we may term normal 

 vegetation. The key-note to his treatment of these four 

 divisions is given in the ideal which he keeps before 

 him, that of ascertaining the manner in which each type 

 and each species places itself in harmony with its surround- 

 ings by means of morphological, anatomical, and physio- 

 logical differentiation and adaptation. The book is 

 essentially one of classification of these adaptations, and 

 of the varied environments inhabited by plants, and it 

 is one which ought to be read not only by botanists, but 

 by all who care for the general questions concerning the 

 distribution of living forms in water and on land. 



J. B. F. 



OUR BOOK SHELF. 



Rivers and Canals. The Flow, Control., and Improvement 

 of Rivers, and the Desigti, Construction and Development 

 of Canals, both for Navigation and Irrigation ; "with 

 Statistics of the Traffic on Inland Waterways. By 

 Leveson Francis Vernon-Harcourt, M.A. In 2 vols. 

 Vol. i.. Rivers; vol. ii.. Canals. 651 pp. and index; 

 with 13 plates of illustrations. (Oxford : Clarendon 

 Press, 1896.) 

 The first edition of Mr. Vernon Harcourt's book on 

 rivers and canals was published in 1882, and has been 

 regarded as one of the standard books on the subjects of 

 which it treats. The present edition is not merely a 

 revise of the former one, but has been almost entirely re- 

 written, and the subjects rearranged and brought up to 

 date. The wide experience which the author has had, 

 from being frequently called upon professionally to in- 

 vestigate and report on matters relating to rivers and 

 harbours, and the active interest he has taken in the 

 various navigation congresses which have been held in 

 this and other countries during the last few years, fully 

 entitle him to write with authority on the theory of river 

 engineering, and the principles to be observed in carrying 

 out works of improvement. The theoretical part of the 

 book is supported by descriptions and illustrations of the 

 chief works which have been carried out for the control 

 and improvement of rivers, and the construction of 

 canals. The book is written in a style that is thoroughly 

 readable, and is not encumbered with detailed facts and 

 information which, although of great value to an 

 experienced engineer, are not required by a student or 

 reader who wishes to become acquainted with general 

 principles. On the whole, as would naturally be expected, 

 the views expressed by the author are sound, and such as 

 have recei\-ed general acceptanceby the most experienced 

 engineers of this and other countries. There are, how- 

 ever, some matters dealt with on which engineering 

 " doctors differ," and in these cases Mr. Vernon Harcourt 

 would, perhaps, have added to the value of his book if he 

 had given a little more credit to the views of other 

 engineers who have devoted their attention to the same 

 subject. The illustrations are very clear and effective, 

 and add considerably in elucidating the descriptions in 

 the text. In fact, both the author and the publisher 

 deserve the thanks of the engineering profession for 

 bringing up-to-date a work bearing on the management 

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 prosperity of the navigation and commercial interests of 

 this country so largely depend. 



