36 INTRODUCTION 



this line has a growing season of 153 days or less, everything south 

 of it a growing season of 164 days, or more, usually much more. 

 This arbitrarily drawn line seems to separate, roughly speaking, 

 the northern plants from those more generally distributed. Of 

 course there are many exceptions, but, so far as our area is con- 

 cerned, it marks the southern limit of present distribution for 

 many of our plants. The list of plants in paragraph 8, that are 

 marked with an asterisk, are all plants that are found to the north 

 of this line. They are all plants of the higher elevations of our 

 range which, as it happens, are correlated with the shorter growing 

 season. There are, however, no true alpine conditions to be found 

 in this area. 



63. In making use of this factor of the length of the growing 

 season in the body of the work, the writer has added to the treat- 

 ment of the distribution of each species on the different geological 

 formations, two figures, thus: 117-220 days. This indicates that 

 the species under discussion has been found, in our area, in regions 

 with these extremes of growing season. It actually means that 

 this particular species has been found from the Catskills to Cape 

 May. In many species, one of these figures will be in bold faced 

 type which, throughout the book, indicates that the species is more 

 common in the region where the growing season approximates the 

 bold-faced figure than elsewhere. The map {pi. 5) will have to 

 be consulted, until one becomes familiar with these figures, in 

 order to properly interpret this data. 



Summary 



64. The relationship of the edaphic and climatic factors treated 

 in the preceding paragraphs is an exceedingly complex one. To 

 what proportion of either of these sets of factors, or to their 

 combination, is to be attributed the distribution of any particular 

 species, it is practically impossible to say. All that can be at- 

 tempted is to set down the facts so far as we now know them. It 

 is quite obvious that in a book such as this, the introduction to 

 which is mostly, and the body of the work wholly, devoted to 

 floristic plant-geography, the minute study of smaller categories 

 of vegetation, such as associations and the like, must be omitted. 



The study of a flora from the standpoint of its fitness for its 

 environment, and the intimately related study of the environment 



