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 a similar 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, B, and D the 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 a number 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 ly. (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-- 



