8 Charles E. Bcsscy 



Silver Maple (Acer saccliariimm L.) occurs abundantly in the 

 Missouri forest area from which it has extended up the Missouri 

 River nearly to the mouth of the Niobrara River (43) and west- 

 ward fifty to sixty miles, in the moist lands along- the streams. 



Box Elder or Ash-leaved Maple {Acer ncgundo L.) grows 

 abundantly in the Missouri forests, from which it has extended 

 across the state (44). As this species occurs in the Rocky 

 Mountains from New Mexico northward it is possible that some 

 of the trees in western Nebraska have come down from the 

 mountains and met those disseminated directly from the eastern 

 forest areas. 



Iron wood (Osfrya virginica (Miller) Willd.). The small nut 

 is enclosed in a bladdery bag, which is so much larger that it 

 serves the purpose of a wing. A dozen or more of these are 

 aggregated into a loose strobilus. The obvious purpose of this 

 structure is the easy transportation of the seed by the wind either 

 in the whole strobilus, or the separate seed-bearing bags. The 

 tree is abundant in the Missouri forests, from which it has ex- 

 tended up through the eastern and northern counties to Brown, 

 Cherry and Sioux counties (63). 



Water Beech (Carpinus caroliniana Walter.). The small nut 

 is attached to a foliaceous, somewhat three-lobed bract, which 

 serves as a wing. These bracts are not crowcled into a strobilus, 

 but constitute a loose raceme. On falling from the tree the 

 bracts serve to float the seed in the wind for some distance from 

 the parent tree. This species occurs in the Missouri forests, 

 and has been reported from eastern (Sarpy County) and northern 

 stations (Brown County) in Nebraska (64) to which it has ap- 

 parently extended its range. 



The Birches {Betiila spp.). The little nut is winged on its 

 margins. These grow in small cones, from which when mature 

 1:hey are shaken out by the wind, and carried away some distance 

 htiort reaching the ground. 



Canoe Birch (Betitla papyrifera Marshall). This tree occurs 

 in Minnesota and Montana, the Black Hills of North Dakota, 

 :and at a single station on the Iowa River in central Iowa (Hardin 

 County). In Nebraska it is found only on the bluffs and in the 



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