276 FORESTS AND TREES OF KORTH AMERICA. 



Pacific, as is shown by Lieutenant Maury in his Physical Geography 

 of the Sea, though he makes the rains come down entirely too far to 

 the south in regions known to receive but little. 



3. A few words on Florida will show its peculiarities in relation to 

 trees and climate. The trees of Georgia extend for a long distance, 

 some of them continuing as prevailing forms almost to its extremity. 

 But they are gradually replaced by more tropical species, although 

 where the most marked line of distinction exists is not well known. 

 Most of those in the special list have been yet found only on Key West, 

 but the examination of the almost unexplored interior, especially the 

 Everglades, will doubtless extend their range materially. Forty-eight 

 out of seventy-eight species found in it are evergreen, and all but four 

 of these the broad-leaved tropical forms. 



Towards the middle of the State are found extensive prairies and 

 treeless tracts, which are evidently connected with the alternation of 

 wet and dry seasons, generall}'' well marked in its climate. Though 

 the wet season is in summer, yet the little interruption of growth by 

 cold at other seasons makes their dryness influential. Its effects will 

 be hereafter more fully alluded to. 



4. Now coming to the Campestrian Province we find, as already 

 stated, that no new forms of trees appear, while those found rapidly 

 diminish and disappear towards the west. Thirteen species have not 

 been traced west of its eastern border ; about ninety extend pretty 

 far into the Texan and Illinois regions, but only five or six get across 

 the eastern limit oftheCamanche andDacotah regions, which, however, 

 receive nine or ten more from the west and north. 



The Saskatcheivan region, bordering close upon the well- wooded La- 

 custrian Province, may have a few more eastern species, and possibly 

 more from the west, as there is evidence that it is better watered and 

 .approaches in character to the Illinois region. 



It will be observed that the southeast and northeast borders of this 

 province form nearly a right angle with each other, and extending 

 east into Michigan cause a wide separation of the Lacustrian and Apa- 

 lachian provinces. This is one of the most well defined facts in the 

 distribution of trees. A careful examination of the minute land office 

 surveys has shov/n that the line is exceedingly distinct in Wisconsin 

 and Minnesota, prairies prevailing to the south of it interspersed with 

 -oak-openings and groves of deciduous trees along the streams, while 

 to the north pine and spruce forests with tamarack swamps cover the 

 yrhole country, having the other Canadian trees with them. This is 

 doubtless in great part due to the change in the character of soil and 

 of the underlying rocks, which retain the moisture, while it is com- 

 pletely drained ofP to the south. Thus we have here a distinct divi- 

 sion of the two eastern forest provinces, assisting to determine where 

 it would be eastward were it not disguised by local irregularities of 

 surface. 



The cause of the disappearance of trees in the Campestrian Province 

 is, in a word, the deficient and irregular supply of moisture. I need 

 not enter into the proofs of this, but refer to the records of meteorolo- 

 gists. It is true that this does not materially affect agriculture in 

 the more eastern regions ; in fact, most crops will succeed better with 



