IV PREFACE. 



Trees may be occasionally spontaneous over a large area 

 without really forming a constituent part of the flora. Even 

 the apple and pear, when originating spontaneously and 

 growing without cultivation, quickly become degenerate and 

 show little tendency to possess themselves of the soil at the 

 expense of the native growths. Gleditsia, for example, while 

 clearly locally established, has with some hesitation been 

 accorded pictorial representation. 



The geographical distribution is treated under three heads : 

 Canada and Alaska ; New England ; south of New England 

 and westward. With regard to the distribution outside of 

 New England, the standard authorities have been followed. 

 An effort extending through several years has been made to 

 give the distribution as definitely as possible in each of the 

 New England states, and while previous publications have 

 been freely consulted, the present work rests mainly upon 

 the observations of living botanists. 



All descriptions are based upon the habit of trees as they 

 appear in New England, unless special mention is made to 

 the contrary. The descriptions are designed to apply to 

 trees as they grow in open land, with full space for the 

 development of their characteristics under favorable condi- 

 tions. In forest trees there is much greater uniformity ; the 

 trunks are more slender, taller, often unbranched to a con- 

 siderable height, and the heads are much smaller. 



When the trunk tapers uniformly from the ground upward, 

 the given diameter is taken at the base ; when the trunk is 

 reinforced at the base, the measurements are made above the 

 swell of the roots; when reinforced at the ground and -also 

 at the branching point, as often in the American elm, the 

 measurements are made at the smallest place between the 

 swell of the roots and of the branches. 



A regular order has been followed in the description for the 

 purpose of ready comparison. No explanation of the head- 

 ings used seems necessary, except to state that the habitat is 

 used in the more customary present acceptation to indicate 

 the place where a plant naturally grows, as in swamps or upon 

 dry hillsides. Under the head of " Horticultural Value," the 



