6 HARPER 



In the present work, which is a study of the vegetation of a 

 small and in many respects homogeneous portion of temperate 

 Eastern North America, the first stage of investigation above 

 defined has been worked out as completely as time and other 

 limitations would allow. In the second and third stages not so 

 much has been done, but some of the more obvious correlations 

 between different sets of phenomena are pointed out, which is 

 always a step in the direction of explaining their causes. 



The region is first located with reference to other parts of the 

 world, and its distinguishing characteristics described. The 

 vegetation is then classified, first according to habitat, then 

 taxonomically as in ordinary systematic works, and to some 

 extent according to structure. For each habitat group the 

 environmental factors are indicated as accurately as possible 

 without quantitative measurements, and some attention is paid 

 to development and adaptations, as well as can be done without 

 resort to experimental methods. In the taxonomic classification 

 the local and general geographical distribution and habitat re- 

 lations of each species are discussed as fully as space and existing 

 knowledge will permit ; and throughout the work the geograph- 

 ical significance of the facts observed is kept constantly in mind. 

 The characteristics of the habitats, and the ranges and other 

 attributes of the plants, are summarized at the proper places, 

 by means of diagrams and tables wherever possible, to facilitate 

 comparison. In certain parts of the work some observations 

 are recorded which may seem to have little or no significance 

 at present but will in all probability be explained by future re- 

 searches, either in this or in other regions. 



