PREFACE vii 



ances for those who have had particular topics. Again, 

 although I have tried to utilize the best in the experi- 

 ence, of my fellow-teachers (including the very valuable 

 Report of the Committee of Ten) as well as in my own, 

 yet the subject is so new that much discussion, trial, 

 and experiment will be needed before the best selec- 

 tion and proportioning of subjects will be found. 



It will be noticed that the plan of the course does not 

 aim directly at what most of our leading teachers now 

 regard as the ideal. This ideal places vital phenomena 

 first, especially as they manifest themselves in mould- 

 ing the physiognomy of vegetation. Indeed, I sup- 

 pose most people will agree on this point, that the best 

 knowledge we can give our students is that which will 

 enable them to understand the influences determining 

 the physiognomy or topography of vegetation, why it 

 has the shapes and colors and sizes and distributions 

 it has. Our courses should aim to do for the students 

 of vegetation much the same that the modern science of 

 physiography is doing for students of the forms of the 

 land, - - it should demonstrate the factors determining 

 its present construction. But a course aiming directly 

 at this ideal is not at present practicable, and indeed 

 I doubt if it ever will be. The problem of the topog- 

 raphy of vegetation is enormously more complex than 

 that of the topography of the land, and we have not yet 

 either the knowledge, the methods, or the inclination to 

 attack it directly in general courses. It should be kept 

 in view as an ideal and worked toward indirectly. The 

 best basis or skeleton for an elementary course is, and 

 I think always will be, not phenomena, which are ab- 

 stract and elusive, but structure, which is concrete, and 



