RECOGiNITION OF CHARACTER OF SOILS. 499 



short twigs bearing tufts of leaves ; thus forming an open head, 

 in which no creature can hide effectually. On the brown-loam 

 table-lands, again, the post oak has a straight, rather slender, 

 excurrent trunk with long and more or less crooked limbs pro- 

 jecting at a large angle, sometimes even drooping, and freely 

 divided up into lateral, leafy branches; the trees attain from 

 40 to 55 feet in height. Again, on the high sandy ridges 

 which are interspersed in the eastern portion of the brown loam 

 area, we find, generally associated with a similarly depauper- 

 ated form of the black-jack oak, and with the Upland Wil- 

 low oak ( O. ciiierca), a form of the post oak intermediate be- 

 tween that of the Flatwoods and the Table lands ; twelve to 

 fifteen feet high, with thin trunk, " sprangling " long, crooked 

 branches, clothed with sparse tufts of leaves. These four 

 strikingly distinct types are shown schematically, in their ex- 

 treme development, in the subjoined figures. 



It is hardly necessary to say that between these extreme 

 forms there are many degrees of transition, corresponding to 

 the transitions between the several soil-classes respectively rep- 

 resented by them; or they may be developed into depauperated 

 types. Thus, for example, the forms of the post and black-jack 

 oak found on the sandy ridges of the yellow loam region, 

 hardly need experience in the observer to interpret them as 

 characterizing a wretchedly poor soil. 



Forms of the Black-jack Oak. Xot les-^ striking are the 

 characteristics of the forms of the black-jack oak as developed 

 upon these several kinds of land. The black-jack of the prai- 

 ries is a low tree with a dense rounded head, often somewhat 

 flattened above, and a low, thick-set trunk divided up into 

 square-set branches, so densely clad with foliage that no light 

 penetrates into the interior, and birds can safely hide and nest 

 within it. The height rarely exceeds 35 feet, the head being 

 20 to 30 feet across. 



The Flatwoods form, on the contrary, rarely exceeds i; 

 feet in height, with a very rough bark and a small, rather 

 dense, rounded top. giving the whole the appearance of a small 

 apple tree. Practically the same form is seen on poor, clay 

 ridges of " hogwallow " land. 



On the brown-loam lands the black-jack, like the p<>st oak, 

 has a rather slender, often somewhat crooked, but excurrent 



