136 
IOWA ACADEMY OF SCIENCE 
The area first came to my attention during a visit to Des 
Moines about the middle of May, 1914. At that time the work 
of excavation and grading was just being finished, and though 
the growing season was, of course, well begun, there was little 
or no sign of vegetation on any part of the embankment. The 
sandy loam of the levee proper, the half-and-half mixture of 
its western end, and the sand hills on the opposite shore were 
alike as bare and lifeless as a desert. 
A month later I returned to Des Moines, this time to stay all 
summer. I was struck with the remarkably changed appearance 
presented by the surface which had been so devoid of anything 
green only a few weeks before. A vigorous stand of wild grasses 
and of those hardy pioneer plants that most people contemptu- 
ously term weeds had made its appearance and like an army 
was overrunning the territory. On the parts of the work which 
had been finished first the plants stood close and dense, push- 
ing ahead vigorously to overcome their handicap of a late start, 
and, young as they were, already beginning the eternal strug- 
gle for a place in the sun.. On the sandy western end of the 
levee where the ground was poorer and where the steam shovel 
had longest postponed the start there was a straggling advance 
guard, but the sand heaps on the opposite shore remained bare 
and unattacked. Only here and there, where a chance streak 
of loam in the matrix of sterile sand had received a chance seed 
did any green leaves show themselves; here they were mostly 
pigweed, Amaranthiis retrofleoous. 
As the summer advanced these relative densities of vegeta- 
tion maintained themselves much as they were in the beginning : 
on the sand dunes there was little growth, on the ungraded 
western end of the levee there was a fairly well-developed flora, 
and on the levee proper the growth was thick and rank. I 
took occasion to visit the place frequently during the summer, 
and from time to time carried home a handful of specimens, so 
that by the time the first frosts began to take their toll of my 
weed garden 1 had botanized the whole area pretty thoroughly. 
From an ecological viewpoint, the area falls naturally into 
three rough divisions, along the lines indicated above. First, 
there are the sand heaps of the north shore ; then the ungraded, 
sandier part of the levee toward the west, and finally the graded 
levee composed of rather better soil than either of the two pre- 
ceding portions. 
