506 



SOILS. 



Loii'land Tree Growth. The variations occurring in the val- 

 leys or alluvial bottoms are less obvious to superficial observa- 

 tion, yet equally important and cogent to the close observer. 

 In the properly alluvial lands, one dominant condition, that of 

 adequate moisture supply, is almost always fulfilled, irrespec- 

 tive of soil quality. In addition to this, as stated in chapter 

 2 (see page 24), practically all the alluvial lands of the 

 humid region may be considered as being of a more or less cal- 

 careous character, as compared with the adjacent uplands. 

 These two important conditions dominate in a great measure 

 the minor ones of variation in soil-texture. Yet where, as 

 is largely the case in the southern part of the State of Missis- 

 sippi, the amount of calcic carbonate is insufficient to overcome 

 the sourness of the soil, the vegetative contrasts become ex- 

 tremely striking and characteristic, as explained above. 



Contrast Between "I : irst" and "Second' Bottoms. A 

 very striking phase of transition between the alluvial bottoms 

 and the uplands proper in the Cotton States are the second bot- 

 toms or hammocks of the streams, whose soil and tree-growth 

 in most cases differ markedly from those of the first bottom; 

 and these being usually closely adjacent, often afford a very 

 striking contrast to the latter. From some antecedent geologi- 

 cal cause not fully understood, these hammocks, usually ele- 

 vated from 4 to 10 feet above the present flood plain, have 

 almost throughout soils of a line sandy, pulverulent or silty 

 nature, frequently in strong contrast to heavy clay soils in the 

 first bottom. 



They seem, moreover, to have been at M .me time subject to 

 prolonged maceration under water, resulting in the reduction 

 ( f the ferric oxid, and its accumulation in the lower portion 

 of the deposit in the form of bog-ore spots or " black gravel." 

 Since such a process always results in the abstraction of phos- 

 phoric acid from the general mass of the soil, to be accumulated 

 in the bog ore in an inert condition. 1 these hammock soils, 

 usually whitish or gray in color, are almost throughout poor 

 in phosphates as well as in lime; the latter having been defini- 

 tively leached out. The resulting vegetation, as may be 

 imagined, is widely different from that of the bottom proper, 



1 See Chapter 2, p. 24. 



