140 
IOWA ACADEMY OP SCIENCE 
within a few hours after they leave the tree, or else perish. Again, 
the seeds of many of the weeds, like the Amaranths, Chenopo- 
dium, Oxalis, Datura, the grasses, and in fact most of the plants 
on the levee, if not winged are at least small and light and could 
be carried through the air like grains of dust or sand. Some 
of the plants, like Amaranthus, Chenopodium, Abutilon, and 
Datura, hold a goodly portion of their seeds in the previous 
year’s seed-head until well into the following season. And the 
universal distribution of the vegetation over the surface of the 
levee, and even on the heaps of sand from the deeper parts of 
the excavation, must argue for some impartial distributor like 
the wind. 
In brief summary, then, we have the following facts: (1) 
On the sand heaps of the north shore and on the sandier por- 
tions of the western end of the levee, which presented poor op- 
portunities for vegetation on account of the lateness! of their 
exposure to seeding, their natural sterility, and the fact that 
they came from the deeper portions of the cut and hence had in 
themselves no seeds or root fragments., there were few plants, 
and these exclusively from seeds presumably sown by the wind. 
(2) On the more loamy patches at the western end of the 
levee the conditions of vegetation approached more nearly those 
of the eastern portion, or levee proper, though the vegetation 
was still practically exclusively in its first year from seed, that 
is, annuals and seeding perennials. (3) On the best soil of 
the whole area, that of the eastern portion of the levee, the vege- 
tation reached its best maturity, and here it consisted not only 
of annuals and seeding perennials, but also of growths of per- 
ennials in their original position, or from tree stumps, or root 
scraps, and included as well one biennial in its second year of 
growth and a number of cultivated plants and a. few natives 
whose seed probably had been sown by agencies other than the 
wind. 
Of the fifty-six species collected over the whole area, six 
(seven, if Andropogon halepemis be an escape) were cultivated 
plants recently escaped, and the balance native or naturalized. 
Of the cultivated plants, Zea mwis and Andropogon lialepensis 
probably were from feed dropped by horses, Ipomoea purpurea 
possibly was wind-sown, though possibly also of a common origin 
wfith the other four cultivated species, namely Ly coper sicum 
esculenium, Petunia sp., Gitrullus vulgaris, and Helianilius 
