GYMNOSPERIVLE. 107 



RETROSPECT. 



HISTORY OF THE GYMNOSPERMS. 



The imminent publication of more than one work on the evolution of plants led me 

 to defer the detailed sketch of the history of the Gymnospermse, which would have found 

 an appropriate place in the Introduction to the present volume. Viewed from an 

 evolutionary standpoint the Gymnospermous plants assume an importance out of all 

 proportion to the position they occupy in classifications based on living plants, or to 

 their numbers and variety at the present day. They comprise and reveal to us many 

 of the stages traversed between the Cryptogam and the Angiospermous Phanerogam, and 

 alone bridge over the vast interval between these most widely separated divisions of the 

 vegetable kingdom. 



In endeavouring to trace the stages through which the progressive evolution of plants 

 has been accomplished, we must beware of assuming that every less complex organisation 

 is necessarily of greater antiquity than all those which are more highly developed. 

 Combinations of circumstances exceptionally favorable to certain groups of plants have 

 sometimes forced on their development to a state never afterwards surpassed, but which, 

 on the contrary, may have retrograded by the dropping out of prematurely developed 

 types. New series, however, have perpetually branched off to replace those eliminated, 

 and the great vegetable kingdom has thus, as a whole, uninterruptedly progressed. 



Before quitting the Coniferae it is necessary, in order to make clear the relative position 

 in a progressive series which they occupied, to say a few words on the lower forms of 

 vegetative life. The study of the British Tertiary Elora has so far thrown little additional 

 light on the evolution of the Coniferae, and the present brief sketch of their past history 

 is therefore mainly compiled from the works of other and more distinguished authors, 

 to whom I take this opportunity of expressing my deep obligations. 1 



1 I am greatly indebted to Prof. W. C. Williamson, who has kindly revised the sheets relating to Palaeozoic 

 plants, and for the use of his numerous and most valuable papers on Carboniferous plants in the ' Philo- 

 sophical Transactions of the Royal Society ;' to Mr. Carruthers for his many valuable suggestions and 

 the information contained in his numerous works on fossil plants ; to Saporta's magnificent work in 

 the ' Paleontologie Francaise,' 2me serie, " Vegetaux fossiles," on the Plants of the Jurassic Formation : 

 and Saporta and Marion's " Evolution du Regne Vegetale," Phanerogames, vol. i, ' Bibliotheque Scien- 

 tifique Internationale,' 1885. The full details of the theory of plant evolution, which I have attempted 

 to sketch, though with considerable modification, are given in this work. The information derived from 

 these authors is the basis of so much that I have written in these pages, regarding the older plants, that a 

 general acknowledgment of my indebtedness to them must suffice. 



I have also extracted much information from Bentham and Hooker's ' Genera Plantarum ;' Sack's 

 ' Text-Book of Botany ;' various papers by Sir William Dawson ; Schimper's ' Paleontologie Vege'tale,' &c. 



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