389 
editor of a posthumous work has always a delicate position to fill, 
as he is constantly called upon to choose between allowing real 
or apparent errors to remain or correcting them to the best of his 
ability and perhaps making the author say what he never in- 
tended to say. In this volume the editor has adopted a conser- 
vative course, preferring to suffer criticism from modern purists 
rather than to alter the manuscript, or known preferences of 
Prof. Lesquereux except in cases where errors of importance 
were manifest. A short sketch of the life and work of Prof. Les- 
quereux is included in the author's preface, whrch is followed by 
an account of the discoveries in various localities of the flora rec- 
ognized as belonging to the Dakota group. An interesting gen- 
eral discussion or analysis of the flora occupies about thirty pages 
in which attention is called to the significance of many of the 
facts involved. There is no doubt that many of the problems 
connected with the study of the geographical distribution of 
plants at the present day could be solved, at least in a large 
measure, by a careful comparison of the extinct flora with that 
now in existence in the same locality and the more nearly we 
approach modern times the more significant are the results which 
are obtained. Thus in regard to the present work the author 
says: ‘Already the evidence obtained from the study of the 
Dakota Group remains warrants the conclusion that the flora of 
North America is not at the present epoch, and has not been in 
past geological times composed of foreign elements, brought to 
this continent by migration, but that it is indigenous. Its types 
are native; the diversity of their representatives has been pro- 
duced by physical influences; their affinities, therefore, or the re- 
lation of their modification or derived forms can not be looked 
for in the vegetation of distant countries.” To the botanist the 
principal interest will center in the Dicotyledones, which consti- 
tute the bulk of the work. Most of them are referred to living 
genera or genera so nearly allied that their affinities are indicated 
by such names as Rhamunites, Celastrophyllum, Menispermttes, 
Palaocassia, Viburnites, Populites, etc., early ancestors of our 
familiar trees and shrubs of to-day. In this connection, from 
among the many interesting examples, attention might be called 
‘particularly to the species figured under the genus Lirtodendron, 
* 
