DISTRIBUTION OF VEGETATION IN UNITED STATES. 47 



range are shrubs in another. It is also well known that a number of 

 trees which are evergreen in southern latitudes are somewhat decid- 

 uous near the northern limits of their ranges. 



Evergreen broad-leaved trees are found in the United States only 

 on the Pacific coast, in the mountains of the extreme Southwest, and 

 in the southeastern portion of the United States, reaching their greatest 

 abundance in peninsular Florida. Those of the Pacific region are 

 either confined to the Pacific coast of the United States or are found 

 only in extreme northwestern Mexico. The evergreens of the south- 

 western mountains are largely trees which have the major portion of 

 their range in the Sierra Madre region of Mexico. Those of the south- 

 eastern United States are partly peculiar to that region and partly 

 trees of wide distribution in the West Indies, this being notably true 

 of those found in extreme southern Florida. In the western states the 

 greatest extension given the area of this growth-form, at least to the 

 north, is due to the extended range of Arbutus menziesii. In the east 

 the maximum extension of this type is due to the ranges of Ilex opaca 

 and Magnolia glauca, which extend north in the Coastal Plain as far 

 as Massachusetts. The member of the southeastern group which 

 extends farthest west is Quercus virginiana, which is found in western 

 Texas. The inclusion of the evergreen shrubs Rhododendron maximum 

 and Kalmia latifolia would have extended the region of occurrence of 

 this growth-form into the southern Alleghenies and farther into the 

 Northeastern States. With the exception of these shrubs, the ever- 

 green habit is rather poorly represented among the shrubs in the 

 deciduous-forest region, although the evergreen broad-leaved habit 

 again appears in the north as characteristic of numerous bog shrubs. 



In the construction of the map of cumulative occurrence of broad- 

 leaved evergreens 129 species have been used. Of these species, 25 

 occur in Cahfornia and the Southwestern States, 25 in the Eastern 

 States exclusive of peninsular Florida, and 79 in the last-named 

 region. The western and eastern groups do not overlap, except in so 

 far as Quercus virginiana is sometimes found in western Texas in the 

 same region with evergreen oaks characteristic of the Mexican Cordil- 

 lera. Our eastern group of evergreens merges into the group for 

 peninsular Florida in a manner which it is impossible to describe accu- 

 rately on the basis of existing literature. Several of the evergreens of 

 the Southeastern States do not range to the extreme southern end of 

 Florida. Twelve of our 25 eastern species have been eliminated with 

 certainty from the number credited to southern Florida. Out of the 79 

 species which we are listing for peninsular Florida, only 65 are found 

 in the Everglade region exclusive of the keys, while 26 are confined 

 to the keys and their adjacent shores. The complicated distribution 

 of many of these trees in peninsular Florida has made it necessary 

 for us to map that region in a somewhat conventional manner. 



