PREFACE. 



THIS book has a threefold purpose. First, it aims to lead 

 students through a good laboratory course in Plant Physiology. 

 Second, it seeks to provide a handbook of information upon all 

 phases of Plant Physiology having any educational interest. 

 Third, I venture to hope that it may find service as a guide to 

 self-education by ambitious teachers or students, who, unable 

 to obtain regular instruction, yet wish to advance themselves 

 in this attractive and important subject. To meet these ends I 

 have tried to bring together the best of that which is already known 

 in its field, and to add thereto some materials derived from new 

 studies. The book is not a compendium of physiological knowl- 

 edge, nor yet, except incidentally, a handbook of investigation; 

 but it is a guide to the acquisition of a physiological education. 

 It is designed as a contribution to educational economy, and 

 as such I wish it to be judged. 



If the book is found to have any special merit in its particu- 

 lar field, this will no doubt consist in its practicability, for, with 

 but few and mostly obvious exceptions, everything in it has 

 been tested repeatedly by my students and myself. In this, 

 as in some other respects, however, the work is uneven, and 

 some parts have been worked out far more carefully than others. 

 The faults I hope in the future to correct and the deficiencies 

 to supply. Nobody can be more conscious than I of its imper- 

 fections, and of. how much remains to be done to put our phys- 

 iological education upon a satisfactory basis. But at least we 

 may feel assured that we are on the right road, and have made 

 a goodly start. 



