i8 CJiarks E. Bessey 



DISCUSSION 



From the foreg-oing statistics it appears that of the seventeen 

 trees whose fruits or seeds are winged thirteen came into Ne- 

 braska from the southeast and four from the west. Of the eleven 

 species with hairy seeds six came from the southeast and five 

 from the west. Of the twenty species with fleshy fruits sixteen 

 came from the southeast, and four from the west. The single 

 species whose seeds are in rolling balls came from the southeast, 

 and all of the species with edible nuts (eighteen) came from the 

 southeast. The significance of tliese facts is not at once very 

 obvious. They do not directly indicate the relative value of the 

 several devices for dissemination, nor do they plainly decide the 

 question of the efficiency of winds, waters, birds, and quadrupeds 

 as carrying agents. Thus the fact that thirteen trees with winged 

 fruits or seeds came from the southeast, and only four from the 

 west, does not indicate the greater efficiency of the south-east 

 winds over those from the west. The fact that there is a much 

 more compact forest area, containing a greater number of species 

 of trees of this kind a short distance southeast of the state, is of 

 far greater importance. The nearness of a vigorous vegetation 

 representing many species makes that vegetation more efficient in 

 invading a territory. The Missouri forests dominate the forests 

 of Nebraska, because they arc near by, and contain many species. 

 This is shown more emphatically in the case of the species with 

 edible nuts, all of which have come from the Missouri forests, 

 where they are abundant. In Wyoming and northern Colorado 

 there are no species of this kind in the sparse forests within a 

 hundred miles of the western border of Nebraska. There are no 

 oaks, hickories, walnuts, or buckeyes in this portion of the Rocky 

 Mountain foothills to move eastward. On the other hand, there 

 are species of trees having hairy seeds not only in the Missouri 

 forests, but also in the canyons of Wyoming, and here we find 

 that almost one-half of our trees of this kind came from the 

 west. It is to be remarked, however, that while five of the six 

 southeastern species have crossed the state, the five western spe- 

 cies have moved eastward only a few miles from the Wyoming 

 line. 



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