84 PHYSICAL GEOGRAPHY 



CHAPTER VIII. 



FOREST TREES AND SHRUBS OF NEBRASKA, 

 WITH NOTES ON THEIR DISTRIBUTION. 



IN the early reports on Nebraska it was represented that some 

 half dozen species of forest trees were native here. Such reports 

 were evidently made at random. It has too often happened that 

 men with a respectable acquaintance with natural history felt com- 

 petent to to describe the physical aspects and flora of a region after 

 going through it on horse back at a gallop. Only after the most 

 painstaking labor of fourteen years have I found many of the species 

 contained in this list. Since my own catalogue of our Flora was 

 published, and after I had given a list of our trees and shrubs to 

 different parties for publication I discovered some additional species 

 within our borders. One of these is the common white walnut or 

 butternut ( yuglans cmerea), that turned up in Dixon County, a 

 few miles from Iona, in a woodland that I had frequently ex- 

 amined before. Simon Baltzley first informed me of its existence. 

 I have no doubt that still more trees remain to be added to our 

 Flora. There are so many sequestered canyons clothed with timber, 

 which no botanist has yet visited, that it would be extraordinary 

 indeed if some of them did not contain species as yet unknown in 

 the State. I have shown elsewhere that in times quite recent, geo- 

 logically, Nebraska was heavily timbered with a varied forest veg- 

 etation.* When the causes commenced to operate that finally re- 

 duced its area to present limits, some of the species retired gradu- 

 ally to such protected localities as favored their perpetuation. One 

 of these causes probably was forest and prairie fires, inaugurated 

 by primitive races, for the chase and for war. Some species are 

 now confined to spots where fires cannot reach them. Another 

 cause was probably the encroachment of the prairie on the timber 

 area, caused by the ground being so compacted by the tread of 

 countless numbers of buffaloes, that tramped out growing shoots, 



♦Chapter on Superficial Deposits of Nebraska. 



