BOOK REVIEWS. 



83 



stem, root, leaf, 'flower, &c., but only a brief description of Mono- 

 cotyledons (pp. 276-279) and of Orchichlamydeae . It is stated that in 

 the sub-group containing Polygonum, Amaranthus, Chenopodium, and 

 Caryopliyllaceae, &c. " insect pollination is established only among the 

 pinks. " The author does not here seem aware of species of Polygonum 

 with brightly coloured or white calyx, nor of the dimorphism of Buck- 

 wheat. The other sub-group is Sympetalae. The fifth chapter treats 

 of Organic Evolution, and deals with Environment, Use and Disuse, 

 Natural Selection, Mutation, &c., which might, perhaps, with more 

 propriety come under Ecology (p. 283-294). 



Part II. — Physiology — contains a brief account of all the usual sub- 

 jects under that head. With regard to transpiration, the author seems 

 to regard it as synonymous with evaporation (p. 321). But as trans- 

 piration is influenced especially by the red and violet rays of light, and 

 evaporation by heat, it would certainly seem desirable to designate 

 the two processes by distinct terms. Apart from this omission, the 

 whole of this section is a valuable epitome of the latest views on photo- 

 synthesis and other functions of leaves, &c. 



Vol. II. is entirely devoted to Ecology, and is a serious attempt to 

 discuss the forms and internal structures of plant-organs, roots, leaves, 

 stems, &c., in conjunction with the external agencies which affect and 

 often change them. Though illustrating the adventitious roots of maize, 

 the author does not appear to be aware that the absence of a tap-root 

 is characteristic of all Monocotyledons, and is one of the numerous 

 features which prove their descent from aquatic Dicotyledons. 



With regard to the Origin of Species, the author is inclined to avoid 

 all appeal to teleology, preferring to regard variations as due to 

 "mechanical causation," and so purposely avoids speaking of 

 adaptation." We think this is a useless self-restriction. One cannot 

 avoid seeing adaptation everywhere in structures for definite uses ; 

 therefore, why not call them such? It commits one to no theory of 

 how the adaptation arises. Sir A. H. Church's word "directivity" 

 is an admirable term, and commits one to nothing when one says 

 " Life directs forces so as to move matter and to make a useful or 

 purposeful structure." 



Taking the two volumes in their entirety, they are very interest- 

 ingly written, and will convey to the student a large amount of matter 

 which will guide him in the right direction by its ecological application 

 of plant hfe. 



"The Forest Trees of Britain." By Eev. 0. A. Johns, B.A., 

 F.L.S. Eevised by Professor G. S. Boulger, E.L.S., F.G.S. Ed. 10. 

 8vo, 431 pp., with illustrations and sixteen coloured plates. (Society 

 for Promoting Christian Knowledge, London, 1912.) 6s. net. 



The fact that this book has passed into a tenth edition is sufficient 

 proof of its popularity, and that, too, in spite of the numerous works 

 on a similar subject that have appeared of late years. Having 

 reviewed earlier editions of the work, we must in fairness say that 



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