Dr J. B. Hulburt on the Forests of North America. 245 
in some places beyond, and in others not to the Mississippi. 
From this to near the Pacific, within the limits of the 
United States, intervene the naked interior plains for nearly 
4000 miles, succeeded on the Pacific coasts by the forests 
of Conifere. From about the 98th meridian west, the 
forests of deciduous trees extend in a north-west direction 
high up into British America, with a belt of low evergreens 
around Hudson’s Bay, and to the east of the northern parts 
of the valley of Mackenzie’s River. 
This vast compact forest, made up mainly of deciduous 
trees, is interspersed with large areas covered with conifere, 
and with others covered with deciduous trees and conifers 
intermixed, and to the south with tropical evergreens. 
These peculiar forests, prairies, and desert areas, no 
doubt express some distinctive features of climate. Two 
conditions of climate—heat and humidity—marked in a 
high degree, seem essential for the development of those 
gigantic forests of deciduous trees. High summer tempe- 
ratures and abundance of summer rains, are characteristics 
of the whole of the area covered by these forests. The 
temperatures for the three summer months over all these 
forest areas within the United States, Canada, and British 
America, are above 65°, and mostly above 67° of Fahr.,— 
temperatures high enough and long enough continued to 
mature maize, or Indian corn, and the grape; for the wild 
vine (Vitis cordifolia) matures its fruit to the northern 
limits of the deciduous forests. Twenty inches of rain in 
the states bordering the Gulf of Mexico, and ten inches in 
the north and through Canada, give, in general terms, about 
the quantities that fall during the three hottest months— 
June, July, and August. Similar high summer tempera- 
tures prevail over the western prairies and interior desert 
areas, but with a partial or total failure of the summer rains, 
and here we find the absence first of all forests, and then 
of all vegetation. On the Pacific coast, in high latitudes 
especially, the summer rains are abundant, but the summer 
temperatures are low, falling to 57° and 60°; and here are 
the most extraordinary examples of the conifere, but the 
deciduous trees are wanting. 
Within the limits of these three great divisions we meet 
NEW SERIES.—VOL. XVIII. NO. I1.—ocTOBER 1863. 21 
