8vo. 18s. net. 



THE ORIGIN OF A LAND FLORA 



A THEORY BASED UPON THE FACTS OF 

 ALTERNATION 



BY 



F. 0. BOWER, Sc.D., F.R.S. 



REUU'S PROFESSOR OF BOTANY IN THE UNIVERSITY OF GLASGOW 



With numerous Illustrations. 



In his Preface the author explains that his interest in the question dis- 

 cussed in the present work has been of long standing ; that it seemed to him 

 probable that some biological cause had determined the prevalence and con- 

 stancy of the alternation, to which apogamy and apospory appear as occasional 

 exceptions. The theory was entertained that the change of conditions 

 involved in the invasion of the land by organisms originally aquatic had 

 played a prominent part in the establishment of those alternating phases of 

 the life-cycle which are so characteristic of Archegoniate plants. As early as 

 1890 Professor Bower briefly stated his theory in a paper published in the 

 Annals of Botany, but his researches have led him to the conclusion that only 

 " now, after the lapse of seventeen years, it has been possible to state the 

 biological argument more fully in the present volume, strengthened by many 

 new facts. The first part deals with the general theory. The second part is 

 taken up with a detailed statement of the facts, together with comparison of 

 the constituents of the several phyla inter se. The third part is devoted to 

 general comparisons and conclusions. . . . 



" The attempt has been made to work in the results of Palaeontological 

 research with those of the comparative analysis of living forms. The enquiry 

 has related to all the characters, both vegetative and propagative, of the 

 sporophyte generation : these include the external form, the embryogeny, 

 and anatomical features, and especially the structure and development of the 

 spore-producing members, while the characters of the gametophyte have also 

 been taken into account. It is found that the conclusions arrived at are 

 supported by general convergence of the lines of evidence derived from all of 

 these sources." 



Professor Bower's important work is a substantial volume of over seven 

 hundred pages, with a large number of illustrations. 



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