PREFACE 



The essays comprised iu this book are selected from 

 popular addresses and articles presented by the authors 

 within the last five years. The unequal conditions of 

 the original preparation have made it necessary to revise 

 and rewrite certain articles in order to meet the require- 

 ments of their juxtaposed position. The occasion has 

 been seized to omit portions less relevant in the present 

 connection, and to amplify others to meet the demands 

 of continuity, clearness, and harmony with current bo- 

 tanical thought. The original presentation of each sub- 

 ject is denoted by a foot-note under the title. The au- 

 thors are separately responsible for the chapters to 

 which their names are signed in the table of contents. 



The publication of this volume, it is believed, is justi- 

 fied by the appreciation accorded the essays, upon 

 their first appearance; and it is the hope of the authors 

 that it may stimulate an interest in the phases of botany 

 covered, both among general readers and also among 

 workers in the co-ordinate branches of animal biology. 

 March, 1898. The Authors. 



