FORESTS AND TREES OF NORTH AMERICA. 279 



Teninsula by natural affinities. Its mountains essentially resemble in 

 climate and forest growth the Lacustrian province. Its valleys are 

 like the Illinois and Texan regions, with this difference : that they 

 have periodic dry and wet seasons, occurring at seasons opposite to 

 those of Florida. Connected with this and with the mildness of its 

 winters we again find a large proportion of broad-leaved evergreens, 

 several genera, as the oaks and chestnut, which are deciduous in the 

 east, being nearly all evergreen there. I should have mentioned that 

 the same is the case in Arizona, though there a climate of tropical heat 

 requires no interruption of vegetation. 



7. The Oregon region, and those north of it, as far as known, have 

 very peculiar characters as well as points of resemblance to the eastern 

 region. The climate is mild and equable, without excessive heat or 

 cold, the rains abundant, and towards the coast excessive, with but 

 short intervals, scarcely amounting to a dry season. The forests, 

 while mostly composed of the northern forms of Coniferae, have also 

 several broad-leaved evergreen trees and shrubs, which give them 

 almost a tropical aspect. Both in climate and vegetation this western 

 coast resembles much the coast of Europe, species and genera of trees 

 being almost identically represented, and in about the same numbers. 

 On the other hand, a similar analogy exists between the Apalachiau 

 forests and those of China. 



The marked differences in the character of the various mountains 

 and valleys in these western regions may in future lead to more 

 minute division than I have adopted, but present information does not 

 warrant it now. Species formerly supposed to be limited to a narrow 

 district have unexpectedly been found in others far distant, but of simi- 

 lar natural character, the intervening wide tracts being entirely des- 

 titute of them. Many facts go to show that the distribution of trees 

 and forests was once very different, and is even now constantly 

 changing, together with the climate; but as even the possibility of 

 this change is doubted by some, except with such geological convul- 

 sions as can upheave mountains and sink continents, we must not be 

 hasty in deciding the question. 



It may be objected to what I have said of the connexion between 

 the cold winds and the constant rains of the Apalachian province 

 that they do not coexist in the northwestern regions, which, together, 

 form the Caurike Province. But there are other causes which pro- 

 duce the precipitation of rain there. One is the cold northivest sea- 

 breeze, which in winter precipitates the moisture brought by the sowf/i- 

 west winds ; the other is the cold air around the peaks of perpetual 

 snow, which in summer produces at night a downward cold current 

 with the same condensing effect. 



Thus the snowy mountains assist to improve the climate, and inter- 

 cept much of the rain which, more to the north, seems to pass over 

 the lower mountain ranges and to reach the Lacustrian province. 



Mi:ch more might be said respecting the connexions of forests and 

 climate, but the general and best known facts are presented so as to 

 lay the way for more complete observations. The provinces and 

 regions may be classified in the following manner as to these con- 

 nexions : 



