Jantjaet 15, 1909] 



SCIENCE 



111 



■crushing accumulation of evidence in that direc- 

 tion also. 



These statements can hardly be regarded as 

 those of an unbeliever, but suggest the possi- 

 bility that Professor Poulton is speaking in 

 Ms essay as a neo-Darwinian, an upholder of 

 the doctrine of the all-sufficiency of natural 

 :selection. 



The latter part of the Huxley article and 

 the remaining three essays are devoted to a 

 ■consideration of the question of insect mim- 

 icry. They are the pieces de resistence of the 

 whole volume, forming, as they do, the most 

 thorough exposition of the significance of in- 

 sect coloration we possess or are likely to pos- 

 sess until the fuller treatise promised by the 

 author is published. In the abundance of 

 illustrations cited and in the keen criticism 

 to which the various cases are subjected the 

 ■essays stand alone, and their usefulness is im- 

 mensely increased by the addition of a list of 

 the mimicking and mimicked forms referred 

 to, and also by the most complete and thorough 

 index to the entire volume that it has ever 

 lieen the present reviewer's pleasure to use. 

 If any points may be selected for special men- 

 tion from a treatise whose general excellence is 

 so high, they are the evidence advanced tending 

 to place the MuUerian theory of common 

 warning coloration on a firmer basis, and the 

 extension of its applicability to a greater num- 

 ber of cases at the expense of the Batesian 

 theory of mimicry. 



What has been said above is intended as a 

 review of the book from the standpoint of a 

 biologist. To non-biological readers the per- 

 usal of every essay will be both pleasurable 

 ■and profitable; pleasurable because Professor 

 Poulton's style is admirable and both his de- 

 scription of facts and his statement of criti- 

 •cisms clear, and profitable because his informa- 

 tion concerning the topics of which he treats 

 is extensive. Accuracy is never sacrificed to 

 an attempt to popularize the subject; such a 

 •defect is unnecessary in the writings of one 

 who has so marked a faculty for the exposition 

 ■of scientific topics in a manner intelligible to 

 the general reading public. 



J. P. 



THE GENERA OP AFRICAN PLANTS 



The agricultural, commercial and industrial 

 activity of Europeans in Africa has been so 

 great of recent years that the interior of that 

 great continent has become to-day perhaps the 

 most eagerly exploited field in descriptive 

 botany, not even excepting the Philippines 

 under American administration. 



Though the British and French pretty 

 evenly divide honors in the earlier study of 

 African botany, and the former are likely 

 long to maintain their lead in knowledge of 

 the Cape flora, other nations have contributed 

 very materially to our knowledge of the dark 

 continent; and despite the fact that England 

 was the first to press into the tropical interior, 

 the present development of the latter has 

 fallen largely to the Germans and Belgians. 



To botanists possessed of collections of 

 African plants, no recent publication is likely 

 to be more directly and frequently helpful 

 than Thonner^i " Bliitenpflanzen Afrikas.'" 

 This stately volume brings together in synop- 

 tical form the scattered skeletal elements of 

 the flora as a whole. Nomenclature, taxon- 

 omy and general ideas of segregation follow 

 the Berlin practise. Well-contrasted keys are 

 provided for the differentiation of families, 

 and, under them, of genera: and the illustra- 

 tions, from original drawings, simplify the 

 application of text-characters. Indexes to 

 popular and Latin names of plants add to the 

 value of the book. 



One of the most interesting features of the 

 manual is a tabulated conspectus of the 

 known African plants, which may be sum- 

 marized as follows : 



Distribution. Families Genera Species 



Total known 285 9,942 136,000 



African 221 3,648 39,000 



Indigenous 213 3,486 38,600 



North African .... 981 4,850 



Middle African ... 2,185 18,300 



South African .... 1,393 13,300 



Insular 1,266 5,950 



^Thonner, P., "Die Bliitenpflanzen Afrikas: 

 Eine Anleitung zum Bestimmen der Gattungen 

 der afrikanischen Siphonogamen," Berlin, Fried- 

 lander, 1908, pp. xvi -\- 673, pi. 150, 1 map. 



