48 BIG SPRING PRAIRIE. 
quereux’s suggestion that the clay in ponds may be 
formed by remains of convervoideae and characeae 
is true. 
The soil in the western part of field is from two to. 
five feet deep with asimilar arrangement of materials, 
but the muck and clay are relatively much thicker. 
In fields B, F, and C the muck is deeper than in A, 
with the exception of the wooded clay island and its im-- 
mediate vicinity. In H,G, E, and Dthe muck is of 
still greater depth. 
Along the Brown Ditch in eastern portion of field 
F, the layers of muck and sandy clay are quite promi- 
nent, while along the ditch in western portion of field 
the muck only, is visible. 
The surface of this field is quite irregular, especially 
the western portion, on account of the ravages of one or 
more severe prairie fires, which left anumber of depres-- 
sions of irregular outline and of varying extent. In. 
1896, these were from one to three feet lower than the 
surrounding portions. 
Before the last deepening of the outlet of the Brown 
Ditch in 1897, these depressions contained more or less. 
water throughout the entire year. Although the Brown 
Ditch was deepened only to the western extremity of 
field A, the remainder of ditch has become deeper by 
natural erosion. In 1899, a tile ditch was constructed 
as indicated on Map II. Asa result, the depressions. 
indicated by the banded areas, contained water only 
during quite wet weather. 
In 1896, Typha latifolia L. (Cattail); Isnardia pa- 
lustris LL. (Marsh Purslane); Proserpinaca palus-- 
tris L. (Mermaid-weed); Scirpus lacustris L. (Great 
Rush); Ranunculus delphinifolius Torr. (Yellow Crow- 
foot); and Carex (various species) were the characteris- 
tic plants, thus indicating the true hydrophytic condi-- 
tions. In 1900, the Typha latifolia was becoming quite 
scarce, while the Ranunculus delphinifolius had entire-- 
