306 THE JOURNAL OF BOTANY 



vol. iv., has here been again revised by Ulbrich, but it will be 

 necessary to consult a further paper by him in Notizblatt Bot. Grart. 

 Berlin-Dahlem, no. 72, for a complete account of the genus. 



Instances of omissions similar to those mentioned could be mul- 

 tiplied, but, as has already been stated, the vokimes form a most 

 important contribution to our knowledge of African plants, and we 

 await the continuation of the work with much interest. 



E. G. B. 



Age and Area, a Studi/ in OeograpJiical Distribution and Origin of 

 Species. By J. C. Willis, Sc.D., F.K.S., with chapters by 

 Hugo de Vkies, H. B. Guppt, P.B.S., Mrs. E. M. Keid, and 

 James Small, D.Sc. 8vo, pp. x, 259. Cambridge University 

 Press, 1922. Price 14s. 



Dr. Willis has brought together in this volume the results of 

 work extending over some 3'ears, with which botanists have become 

 familiar from papers published chiefly in the Annals of Botany, and 

 from various discussions at the Linnean Society, At the recent 

 meeting of the British Association botanists and zoologists joined 

 in a discussion of the present position of Darwinism, which was 

 opened by Dr. Willis, who re-stated the position taken up in his 

 book. Dr. Willis himself presents an interesting case of evolution. 

 Trained at Cambridge in an atmosphere of Darwinism, he began his 

 work as a naturalist, studying the adventive flora of the pollard 

 Willows near Cambridge. His removal to Ceylon gave opportunity 

 for an exhaustive stud}'- in field and laboratory of an apparently 

 highly adapted famil}^ the Fodostemacece, but one which. Dr. Willis 

 concluded, gave strong evidence of absence of particular adaptation. 

 Many genera and species showing striking differences were found 

 living under remarkably uniform conditions. A serious accident 

 which hindered laboratory work led Dr. Willis to the study of the 

 distribution of the components of the Ceylon flora. He found that 

 the endemic species occupied on the average the smallest areas in the 

 island, those found also in Peninsular India, but not beyond, areas 

 rather larger, and those that ranged beyond the peninsula the largest 

 areas of all. The theories that endemic sj^ecies were either local adap- 

 tations, or relics, were considered inadequate to explain the fact that 

 the areas occupied both by endemics and by widely distributed species, 

 were arranged in a graduated series, the first from man}' small to few 

 large, the second in the opposite direction. Some mechanical ex- 

 planation was necessary, and the only simple and reasonable one 

 seemed to be that the area occupied increased with the age of the 

 species; that is to say, if sufficiently large numbers (not less than 

 ten) of allied species are considered, the area they occupy in any 

 given country depends on their age. Dr. Willis does not deny that 

 there are many factors operating in the distribution of any given 

 .species, but the resultant effect is determined by the age of the 

 species. The same results were obtained with other floras. Further, 

 the area occupied bears a similar relationship to the size of genera; 

 the large genera are widely distributed, the smaller less so. The 

 phenomena of evolution and of geographical distribution may be 



