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jack pine are occasional, the latter along the Wisconsin boundary, and 

 the former extending as far south as Ogle County and the valley of 

 Rock River. Tamarack and arborvitse grow near the northern boun- 

 dary, on low ground. 



Among the hardwoods, the oaks and hickories lead in number of 

 species, in number of trees, and in amount of wood. There are nine- 

 teen species of oaks and nine of hickories. Among the other important 

 genera that are well represented is the ash, with five species widely 

 distributed. All the important maples are included in the five different 

 species, most of which are widely distributed and on the lowlands 

 often form a large part of the forest. Practically all the important 

 species of elm are found in large quantities, the white and red elm 

 occurring throughout the state, while the winged elm is restricted to 

 the south and the cork elm to the north. Among the true poplars, 

 the common cottonwood is very widespread, while the trembling and 

 largetooth aspens are northern species, and the swamp cottonwood 

 is confined to the extreme southern bottoms. The poplars also are 

 often cultivated, and white poplar (Populus alba) and black poplar 

 (P. nigra), which have been introduced chiefly for roadside planting, 

 sometimes escape from cultivation. Lombardy poplar (P. nigra var. 

 italica) is also a common decorative tree, and is very distinctive in 

 form. The willows seldom reach much importance commercially, or 

 from the standpoint of size, but have a wide range and great variety 

 of species. There are two exotics that are commonly cultivated, 

 namely, the white willow (Salix alba) and the weeping willow 

 (S. babylonica). The black walnut was originally both widespread 

 and fairly abundant, but only the smaller sizes are left, and it is very 

 scattered because of the great demand for it in the timber markets. 

 Butternut is also found throughout the state, but seldom grows to 

 large size, and is very sparsely scattered throughout the forests. The 

 principal representative of the birches is the river birch, which grows 

 in the south along the streams. Paper birch occurs in the extreme 

 northern part of the state. Hornbeam and blue beech are very widely 

 distributed. Beech is found chiefly in the cool valleys of the Ozark 

 Hills, but extends north to some extent up the streams, especially of 

 the Wabash River system. Hackberry grows everywhere throughout 

 the state, but most on the southernmost bottomlands. The sugarberry 

 of the same genus is rarely found except as a shrub or bush, and is 

 confined to the south. Mulberry is very scattered, with few large 

 specimens, partly because it is eagerly sought after for fence posts. 

 Osage orange, while out of its natural range, is everywhere very 

 largely used for hedges, and in some places has escaped from culti- 

 vation. The cucumber-tree is confined to the southern hill forests 



