vi PREFACE 



exhaustive bibliography. The matter of selection has often been 

 a difficult one and doubtless references have been omitted which 

 should have been included. For such errors of judgment or of 

 ignorance I must accept the full responsibility. 



At various points in the book it has seemed necessary to extend 

 the consideration into fields more or less remote from those with 

 which I am most familiar. I must frankly acknowledge, however, 

 that some of these ventures into other fields have been attended by 

 the feeling that discretion would perhaps have been the better part 

 of valor, for any venture very far outside one's own little garden plot 

 of scientific thought is likely to be attended by a very decided feeling 

 of strangeness; one realizes that one is not at home. Nevertheless 

 such ventures are necessary if different lines of investigation and 

 thought are to be co-ordinated and synthesized into a harmonious 

 whole. I can only hope that in this particular case the excursions 

 into neighboring gardens and fields have not been wholly fruitless 

 or mistaken. As regards actual errors of statement or reference 

 and other similar matters which may have escaped correction, I 

 can only plead human fallibility. 



It has been necessary, particularly in those chapters which are 

 concerned with the various reproductive processes and with the 

 morphology of the gametic cells, to use figures from various other 

 authors and I wish to acknowledge my obligations for such figures. 

 Figs. 102, 103, 104, 105, 106, 107, A-C, 1 08, 125, 128, 132, 133, 134, 

 135, 136, 137, 138, 139, 141, A-E, are reproduced from A Text- 

 book of Botany by Coulter, Barnes, and Cowles, by permission of 

 the American Book Company, publishers, and Dr. Coulter, the 

 senior author. I am greatly indebted both to the publishers and 

 to Dr. Coulter for permission to use these figures of characteristic 

 morphological and reproductive features of plant life. Figs, in 

 and 112 are reproductions in slightly modified form from Minot's 

 The Problem of Age, Growth and Death, by permission of the pub- 

 lishers, Messrs. G. P. Putnam's Sons. For other figures which are 

 not original acknowledgment is made in the legends, and since it 

 is often highly desirable to know, not only the author of a particular 

 figure, but the publication in which it originally appeared, a refer- 

 ence number, as well as the author's name, is given and the full 



