186 



The lighter-seeded species, such as ash, elm, hackberry, soft maple, 

 and red gum, are usually more scattered, although maple and gum 

 both frequently form thickets where there is plenty of light. Hick- 

 ory reproduces in groups and as individuals. Ash is much more 

 abundant among trees of seedling size than among saplings and poles, 

 as the young trees seem especially subject to disease. Maple, hickory 

 (especially bitternut), ash, and hackberry often grow up under the 

 shade of the mature stand and, becoming more intolerant of shade 

 with age, gradually die off unless released by a cutting. Willow and 

 Cottonwood seldom reproduce except on moist mineral soil, but come 

 up abundantly on sand bars and newly exposed river flats. 



