274 FOEESTS AND TREES OF NORTH AMERICA. 



writer has collected a large amount of material relating to it, winch 

 he hopes at some future time to publish in the form of physical charts, 

 and intends the present paper merely as a circular requesting further 

 information, for which due acknowledgment will always he made, and 

 the favor reciprocated as far as possible. 



. GEKERAL CONCLUSIONS. 



Looking now at the regions as combined in groups, we may derive 

 the following conclusions from the examination of the number of 

 species, abundance and arrangement of their trees and forests. 



1st. Coming southward from the treeless Esquimaux region and 

 passing a certain well marked line, we suddenly find a continuous 

 forest, broken only where the poverty of the soil or other local causes 

 prevent the growth of trees. About fifteen species compose this forest, 

 but the prevailing forms are the Coniferae. For much interesting 

 detail on the influence of climate and other causes on this northern 

 line, as well as for evidence of its encroachment southward, I must 

 refer the reader to Dr. Eichardson's interesting Arctic explorations. 



Passing into the Canadian region we find seventeen species of trees 

 suddenly added as characteristic, and towards its southern border 

 many of those of the Apalachian Province begin to appear. Yet the 

 Lacustrian Province is a well marked one, and in the grouping of its 

 trees differs materially from those farther south. 



Too little is known of the climate,, in its interior especially, as to 

 the amount of rain at different seasons, to form conclusions as to its 

 influence on this peculiar grouping. It appears more probable that 

 other physical agents were the chief ones in this respect, particularly 

 the geographical and geological barriers which those interested may 

 perceive on good maps. Another affecting the western part of the 

 boundary will be hereafter referred to. 



2d. Coming next to the Apalachian Province, and remembering 

 that the forests of a great part of the Alleghenies are only a south- 

 ward extension of those farther north, we find a vast increase in the 

 variety of our forest trees. In fact, looking at all its natural products 

 collectively, one of the most striking, as compared with the rest of 

 the world between the 30th and 45th degrees of north latitude, is its 

 richness in trees, which will compare favorably with almost any part 

 of the troi)ics. 



It contains more than twenty species which have no representatives 

 in the temperate climates of the Old World, and a fjar greater number 

 of species of the forms found there. In fact, those trees which have 

 been considered characteristic of the Lacustrian Province, with perhaps 

 the addition of those of the Allegheny region, will fully represent all 

 the common trees of Europe in number of species, tliough a few 

 other genera must be added from other regions to give them all. 



Yet with all this variety the bulk of tlie Apalachian forests is of forms 

 characteristic of the temperate zone. Only about twenty-three out of 

 one hundred and thirty-six species are broad-leaved evergreens, and 

 these nearly all in the two southern regions. We will hereafter see 

 a marked difference in another part of the continent in this respect, 



