46 MISSISSIPPI STATE GEOLOGICAL SURVEY (Bull. 
Pilea pumila Aspidium thelypteris 
Euonymus Americanus Asclepias perennis 
The Yazoo Delta.—The Delta region embraces all the allu- 
vial lowlands bordering the Mississippi River and the lower 
courses of its tributaries. It is a narrow strip, from one to a 
few miles wide in south Mississippi, but north of Vicksburg, 
Warren County, it widens to a broad nearly level plain 60 
miles wide at its widest part, and about 200 miles in length. 
This plain les so nearly level that the drainage is poor, and 
occasionally much of it overflows. 
The soil is very rich, but presents two well-marked phases. 
Along the streams and for a few miles back the soil is a fine 
sandy loam which les a little higher and is better drained than 
the lands within the interstream areas, where owing to their 
relative lowness and the heavier clay soils, much of the surface 
is permanently occupied by bayous, lakes and swamps. 
These Delta plains were orginally covered with heavy 
hardwood forests, much of which still stands in the low swam- 
py areas. The trees are prevailingly of the moisture and 
water loving kinds, as would be expected, and differ from the 
tree flora of the last described region quantitatively rather 
than qualitatively. While no new species are found in this 
section, the bulk of the forest growth runs much more largely 
to a few dominant species. On the higher, better drained soils 
a fine growth of lowland oaks prevail, with an admixture of ash, 
hickory, pecan, beech, hackberry, and magnolia, with com- 
paratively little undergrowth except along bayous and stream 
channels. In the low swamp areas the tree growth becomes 
predominently a forest of swamp species, mainly of gum (Nyssa 
silvatica, N. unifiora and N. aquatica), red gum (Liquidamber 
styraciflua) and cypress, in dense growth. Cane and palmetto 
palm often form dense undergrowth all but impenetrable. 
In open sand flats near the Mississippi River cottonwood 
is a very common growth, as also is the willow (Salix nigra). 
The herbaceous flora of the Delta is not very varied. The 
shade of the forest is such that few species thrive beneath them. 
A few species not already mentioned as occurring in the adja- 
