SHRUBBY VEGETATION OF CLEARED LAND. 407 



native trees which occupy such habitats can best be included in this 

 formation, unless it is clear that they owe their occurrence directly to 

 human agency. 



The commonest and at the same time the most handsome shade tree 

 of the region is the willow oak. ( Quercus pheUos), which is often planted 

 about farmhouses and along the streets of towns, but also undoubtedly 

 occurs as a remnant of the aboriginal plaid, covering, especially in low 

 ground. This oak is frequently of great size, and, where its environ- 

 ment permits, of beautifully symmetrical form, with wide-spreading 

 branches and rounded crown. Other species of oak, notably the water 

 oak (Q. nigra), the red oak (Q. rubra), the white oak (Q. alba), and 

 the quercitron (Q. velutina), are frequent on plantations. The beech 

 (Fag us americana), the sweet gum (IAquidambar styracifhm), the 

 tulip tree (Liriodendron tulipifera), and, more rarely, the mockernut 

 hickory (Hicoria alba) grow to be magnificent trees when left, stand- 

 ing in the open. The sassafras (Sassafras sassafras), the persimmon 

 (Diospyros virginiana), and the chinquapin (Castanea pumila) occa- 

 sionally attain arborescent size at roadsides. Here, as in other parts 

 of North America, the red cedar (Juniperus virginiana) seems to be 

 most at home along country roads, and is consequently a conspicuous 

 feature of the landscape. 



SHRUBBY ASSOCIATIONS— THICKETS AND HEDGES. 



Fence rows, especially upon land that is not thoroughly cultivated, 

 are commonly occupied by a low, woody growth, consisting of such 

 normally arboreal species as the sweet gum (Liquidambar), the black 

 cherry (Primus serotina), and various oaks; of shrubs, e. g., persim- 

 mon (Diospyros), sassafras, sumac (Rhus copaUina), chicasa plum 

 (Prunus angustifolia), common blackberry (Rub us sp.), etc.; and of 

 lianas, especially species of greenbrier (Smilax), the muscadine grape 

 (Vitis rotundifolia) , the yellow jessamine (Gelsemium sempervireris), 

 the trumpet creeper (Tecoma rod tea its), and the poison vine (Rhus 

 radicans). Where the soil is comparatively rich and moist the elder 

 (Sambueus canadensis) often predominates, and is an exceedingly 

 common plant along roadside ditches. The same association usually 

 occupies the embankments of railways, except in the immediate 

 vicinity of towns. Some of these plants, notably Sassafras, Diospy- 

 ros, and Rhus, are abundant in old fields, and even among standing 

 crops if these are not well cultivated. 



Prunus angustifolia is common in dry, sterile soil at roadsides or in 

 clearings and occasionally forms small dense thickets, growing to an 

 average height of 1 to l\ meters (4 or 5 feet), but is sometimes 3^ meters 

 (12 feet) high, with a trunk 15 centimeters ((') inches) in diameter. 

 The short thorny branches and the rather small and thickish leaves 

 give the plant a distinctly xerophytic stamp. Where the Prunus 



23592— No. <i— 01 7 



