PREFACE 



The present memoir, which I had the advantage of reading in 

 MS. and of fully discussing with the author, seems to me of the 

 utmxDst interest. A survey of these early Floras of the land is a 

 most useful undertaking and one much wanted at the present 

 time, when important new discoveries have called general atten- 

 tion to the plant-life of the Devonian period. Such a survey is 

 all the more valuable, when, as in this case, there is an under- 

 lying theory giving a definite point of view to the exposition of 

 the facts, and animating the whole. 



It is a matter for deep regret that the work never received 

 the final revision of the author, and that he never saw the later 

 results of Kidston and Lang's researches on the Rhynie fossils. 

 As it seems to the present writer, the views of those investi- 

 gators, though differently and more tentatively expressed, are 

 yet in substantial agreement with Arber's, so far as regards the 

 general question of the systematic position of the Psilophyton 

 Flora. However this may be, it must be recognised that Arber's 

 conclusions, which were reached altogether independently, bear 

 the stamp of true originality and are absolutely his own. 



In the Introduction, the author lays down the essential dis- 

 tinction between the earlier and the later Devonian Floras, the 

 former, called the Psilophyton Flora, consisting chiefly of Pro- 

 cormophyta or Propteridophyta, while the latter, the Archaeo- 

 pteris Flora, was chiefly composed of true Pteridophytes. In 

 the first two chapters the geological age and distribution of the 

 two Floras are discussed, and useful tables of genera and species 

 are given. 



Chapter III, "Recent Advances in our Knowledge of the 

 Psilophyton Flora," gives a clear account of^each genus, with 

 the aid of abundant illustrations, collected from various sources. 

 This chapter, and the corresponding one (the fifth) on the 

 Archaeopteris Flora, will be of the greatest value to the student, 



