130 ILLINOIS ACADEMY OF SCIENCE 
section about three years later, while work on the west section 
was started about six years ago and finished four years later. 
The west section because of its recent abandonment is still 
largely occupied by the pioneer ruderal plants. Because of 
the nature of the surface (Fig. 1) both hydrarch and xerarch 
secondary successions are represented. In the bottoms of the 
furrows the two knotweeds, Polygonum aviculare and Polygo- 
num persicaria, are the dominant and often the only plants. In 
the shallower furrows Echinochloa crusgalli, the barnyard 
grass, takes the place of the Polygonum or occurs along with it, 
and often scattering individuals of the giant ragweed, Ambro- 
sia trifida, also are present. 
The ridges present somewhat more variety in their floras 
although some of them are almost exclusively occupied by the 
sweet clover, Melilotus alba. Others, however, are covered with 
such plants as the wild aster, Aster ericoides; sunflower, Heli- 
anthus hirsutus; ragweed, Ambrosia artemisiifolia; evening 
primrose, Oenothera biennis, and occasional individuals of 
_ black mustard, Brassica nigra. On those parts of the section 
that have been longest abandoned one finds also patches of 
venus’s looking glass, Specularia perfoliata, and of partridge 
pea, Cassia Chamaecrista, and occasional individuals of poke- 
weed, Phytolacca decandra. 
The middle section of the area under consideration has been 
subjected to artificial interference which has not made it less 
interesting but has greatly retarded its revegetation. The in- 
terference is due to the fact that the mining company is almost 
constantly pumping water into it so that it is largely flooded 
as shown in Fig. 2. The shallow parts of the water are occu- 
pied almost exclusively by the cat-tail, Typha latifolia. Just 
above the water on the sides of the ridges there is usually a 
zone of cocklebur, xanthium commune. On some of the 
lower ridges the willow, Salix nigra, has become established in 
considerable numbers, while the higher ridges are in most cases 
still occupied by sweet clover, melilotus alba, and black mus- 
tard, Brassica nigra. 
In the eastern section the xerarch and hydrarch successions 
mentioned in connection with the western section have become 
a 
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