AGE AND AREA 307 



represented b}' hollow curves which are always of the same type and 

 are closely parallel in both ])lants and animals. In a word, Dr. Willis 

 lias become a statistician. Evolution and distribution follow strict 

 mathematical laws. 



As regards the origin of species, Dr. Willis accepts the mutation 

 theory, and Dr. de Vries regards these statistical studies, contradict- 

 ing as they do the belief in adaptation as one of the chief causes of 

 the evolution of specific characters, as supplying the one great proof 

 which the mutation theory still wanted for its acceptance in the Held 

 of systematic zoology and, botany. 



Dr. Willis's position met with a good deal of adverse criticism 

 in the recent discussion at Hull. Botanists and zoologists were 

 unwilling to accept a purely mechanical theory of evolution and dis- 

 tribution, and Mr. Kegan, who led the opposition for the zoologists, 

 produced precisely similar curves by taking the frequency of names 

 in a directory, or the sizes of population of towns in an atlas. The 

 curves are obviously the expression of certain facts, the explanation of 

 which must be sought independently in each case. While we may 

 admire the patience and industry with which Dr. Willis has elabo- 

 rated his theory and the courage with which he maintains it, we 

 cannot but hope that after all this is not the conclusion of the whole 

 matter. If species originate by mutation and evolution and distribu- 

 tion are purely mechanical processes, what more is to be done ? 



A. B. R. 



British Basidiomycetce : a Handbook to the lar(/er British Fungi. 

 By Carleton IIea, B.C.L., M.A. Published under the auspices 

 of the British Mycological Society. Cambridge Press, 1922. 

 Pp. xii, 799. Price 30s. net. 



Students of the larger fungi in this country have long desired a 

 manual which would place them abreast of modern work without the 

 constant necessity of reference to foreign literature. The present 

 monograph full}'- meets that need. 



A notable feature of the volume is the breaking away from the 

 Friesian classification. Elias Pries, whose writings on mycology 

 extended from 1815 to 1874, deservedly occupies a similar position in 

 mycology to that of his fellow-countryman Carl Linne in the 

 systematy of flowering-plants. The first British work to adopt his 

 classification was the English Flora, of which Bei-keley wrote the 

 section on fungi in 1836. Cooke's Handbook (1871) sim23ly followed 

 Berkeley ; and the later works of Cooke, Massee, Stevenson, and 

 Smith are based on the Ilymenomy cetes Furopcei (1874). Steven- 

 son's volumes are admittedly translations of Fries's works ; Massee 

 gives a semblance of originality by reversing the order of the genera, 

 but such re-arrangement is not classification. It speaks much for 

 the insular conservatism of our older m3^cologists that, having adopted 

 ** the illustrious Fries," the}^ would not allow in his classification any 

 radical alteration called for by the increasing knowledge of micro- 

 scopic detail. It may be pointed out that it was only in 1837 that 

 Leveille indicated the significance of asci and basidia — at a time when 

 basidia were being figured quite frequently with internal spores! 

 L. K. Tulasne in 1862 showed that the basidia of Tremella and its 



