494 



SOILS. 



Vegetative and Soil Features of the Mississippi Coast Belt. 

 South of the long-leaf pine area lie the coast flats, with sour 

 sandy soils underlaid by stiff clays. On these " pine mead- 

 ows " of the Mississippi coast occur some of the most striking 

 cases of modifications of vegetation due to physical and chem- 

 ical causes. 



As is well known, the long-leaved pine habitually belongs to 

 the dry sandy uplands of the Gulf States; the deciduous cy- 

 press, on the other hand, is most characteristic of the swamps, 

 where its roots are permanently submerged in water. But on 

 the pine meadows of the Mississippi coast we see these two 

 incongruous trees growing side by side, though sadly w r orsted 

 by their mutual concessions ; their heights usually ranging from 

 12 to 15, rarely as much as 18 feet. 1 Yet both preserve their 

 characteristic forms, the cypress being an exact miniature re- 

 production of the usual level-topped swamp form, except as to 

 the " knee " feature; while the pine differs only in stature from 

 its giant brethren of the pine hills, from which it can be traced 

 down through all grades of transition. The soil on which this 

 growth occurs is a sour, sandy one, one and a half to three feet 

 in depth, underlaid by a solid, impervious gray clay, above 

 which is usually found several inches of coffee-colored bottom 

 water, which drains slowly into the sluggish water-courses, 

 themselves carrying brownish, sour, but very clear waters. 

 Analysis shows the soil to be sour and extremely poor, especi- 

 ally in its lime and phosphates (see chapter 19, p. 352) ; its 



1 R. M. Harper, who has graphically described the vegetative features of the 

 coastal plain of Georgia (Contr. from the Dep. of Bot. Colum. Univ. Nos. 192, 

 215, 216, 1902-05; also Bull. Torr. Bot. Club 29-32), claims the deciduous cypress 

 of the wet pine-barrens and ponds therein, the vegetation of which greatly re- 

 sembles that of the pine meadows of the Mississippi seacoast, to be a distinct 

 species, Taxodium imbricarium, the leaves of which are imbricated, instead of 

 two-ranked and with spreading leaflets. He supports this distinction mainly by 

 the differences in habit from the Louisiana swamp cypress, and the fact that the 

 imbricated form occurs wholly on non-calcareous land, while the other is at home 

 in the calcareous alluvial areas. The imbricated form has been observed and 

 commented on before, as a mere ecological variation, and in the writer's opinion 

 this is ail that can be claimed, in view of the much greater differences in the form 

 of other trees, notably oaks, illustrated below, caused also by lime. There would. 

 h fortiori^ be reason for claiming at least three different species of post oak and 

 black-jack (and two of willow oak), which differ not only in tree form but also in 

 the form and number of leaf lobes, and yet can be traced into one another by 

 innumerable transition forms. If new species are to be established on such grounds, 

 it is hard to see where the variations manifestly due to environment are to come in. 



