148 THE FLORA OF MISSISSIPPI. 



region of the northern half of the State lying west of the 

 Flatwoods and east of a belt ten to fifteen miles wide bor- 

 dering the Yazoo-Mississippi Delta. The boundaries may 

 be traced on the sketch map. 



The surface of this region is that of a maturely eroded 

 plateau of varying altitude, from less than 400 to more 

 than 600 feet, the higher altitude being in the northern 

 and eastern parts of the area. Many streams trench the 

 surface, the larger having broad flats 75 to 100 feet lower 

 than the plateau surface. Often one or more terraces 

 fringe the stream valleys. On account of the mature 

 erosion the original plateau has been cut into hills and 

 ridges, the surface being more broken and intricately dis- 

 sected near the larger streams, while in the wider stretches 

 between streams the original plateau presents a gently 

 rolling surface. 



The upland soils of the region are yellowish brown 

 silt loams and reddish sandy loams, with occasional stretches 

 of sticky red clay soils. The silt loams are derived from 

 the Columbian or Brown Loam which caps the plateau 

 surface from five to fifteen feet deep, the sandy loams and 

 red clay soils being derived by the exposure and weathering 

 of the Eocene sands and clays that underly the Brown 

 Loam throughout this region. Plant food is fairly abundant 

 in the silt loam, the sandy and red clay soils being more 

 sterile. The bottom land soils are sandy loams, though 

 some are heavier where the streams receive washings from 

 the Flatwoods. 



The tree growth of this region is very largely pine of 

 two species {Pinus mitis and P. taeda). The forests, how- 

 ever, are not usually pure pine forests, as occur so exten- 

 sively in the southern part of the State, but have a consid- 

 erable admixture of oaks of several species and other hard- 

 wood trees. The hardwood species prevail where the silt 

 loam soil is the prevailing type, the pines being dominant 

 in the other parts, especially in the sandy hills and ridges, 

 which are most common in the eastern parts of the region. 

 The oaks most abundantly mixed with the pines are black 



