THE AX.VTOMr OF WOODY PLAXTS 61 



new derivatives of the still plastic dicotyledons " (p, 41G). Svich a 

 c ;)nsummation, however, is not likely to be reached while Man 

 remains dominant. 



In the chapter on anatomical structure and climatic evolution, the 

 question of annual rings is considered. While the author finds no 

 such rings in Cordaitean wood from Prince Edward Island (lat. 43° 

 80') he believes that the}^ are present in eontemporarv wood from 

 Lancashire (lat. about 5^'' 30'). The difference of latitude seems too 

 small to be significant, and most appearances of annual rinu-s in Car- 

 boniferous woods from any source are fallacious. 



Chap. xxxi. is on a special subject — the evolutionary principles 

 exhibited by the Compositaj — -and is chiefly concerned with the some- 

 what narrow question of the distribution of oil-canals. 



The concluding chapter is on anatomical technique, includino" the 

 sectioning of coal and photomicrographic methods. On all these 

 subjects the author is an acknowledged expert, and his counsels will 

 be of the greatest value to practical workers. 



The index might perhaps have been made fuller with advantao^e. 

 No I'eferences are given in the book; the accumulation of references 

 often becomes a burden, biit a few would have been of service to the 

 reader as a guide to his future studies. 



In the present notice attention has often been directed to points 

 which seem open to criticism or on which there is much difference of 

 opinion. These divei-gences of view in no way detract from a high 

 estimate of the great interest and complete originality of Prof. Jef- 

 frey's remarkable work. 



The illustrations, as one would expect in a book by this author, 

 are abundant and excellent.- 



D. H. S. 



About Fee>\s. 



The question of what constitutes a true species has engaged the 

 attention of Mr. Frederic K. Butters (" Taxonoraic and Geographic 

 Studies in North-American Ferns "—in lihoclora, xix. 1917, pp. 169- 

 21(5). Finding that the commonly accepted distribution of some 

 of the best known ferns is much wider than is usual in the case of 

 j.hanerogams, and that it is often quite at variance with tlie laws 

 of distribution as worked out for phanerogams, he decided to make a 

 critical study of some of the ferns which are supposed to have a very 

 wide and anomalous range. Being of opinion tliat too much reliance 

 has been jdaced on such superficial characters as details in the form 

 and cutting of the fronds, he has deemed it wise to study such 

 technical cliaracters as the size, form and sculpture of the spores, and 

 details of the structure of the sporangia, sori, indusia and scales, in 

 the hope of finding characters of a more stable nature. This investi- 

 gation liMS led to the separation of species and varieties in the ca.se of 

 several CDinmon groups of ferns, and in other cases to the recombina- 

 tion of forms supposed to be distinct : and, as a result, it is found 

 that the fern-species thus reformed have geogr;ii>hical ranges quite in 

 harmony with the Liv.s of distribution ap})licable to plianerogams. 



