PIONEER PLANTS 
141 
ammiiSj which, appiareiitly were remnants of former cnltivations 
cast up by the steam shovel. 
Of the native and naturalized species six were trees and one 
a liane; the rest were herbs. The liane and five of the trees 
sprang from fragments of previous vegetation ; two of the trees 
also appeared as wind-sown seedlings, and one tree only ap- 
peared exclusively as a seedling, presumably also wind-sown. 
Of the wild herbs one was a biennial in its second year, and the 
balance annuals and (apparently) seedling perennials. Of 
these the biennial must have been deposited with excavated 
material, and some of the seeds probably also' came from the 
same source; most of the seeds, however, probably were wind- 
sown. 
I have appended a list of all plants that I found on the area, 
giving also in tabular form such information as I have been 
able to extract from them regarding their age, past history and 
present condition. The classifications were made originally 
from Britton and Brown and afterward checked over and cor- 
rected from Gray’s Manual. I wish to acknowledge mth thanks 
the assistance of Professor Pammel of Ames and of Doctor Con- 
ard of Grinnell in classifying the collection, the latter especially 
also for his valuable suggestions and encouragement in the pre- 
paration of this paper. The following will serve as a key to 
the symbols tabulated at the right of the list. In the first col- 
umn the symbols refer to the position of the plant on the em- 
bankment. signifies that it was found exclusively on the 
top or slopes of the levee, ^^B” that it was found exclusively 
on the flat space at the base, and ‘ ‘ C ” that it grew indiscrimin- 
ately over top, slopes, and base. In the next column the figure 
‘M” indicates an origin from seed. I have listed most of the 
perennial herbs I found under this heading, for though some 
of them may have sprung from fragments of root or stem I 
have no positive evidence that any of them did. ^‘2” indicates 
that the plant in question grew from a stump or root fragment, 
and ‘^3” indicates that some specimens were from seeds and 
others from stumps or roots. In the last column ’^X” indicates 
that the plant was a recent escape from cultivation, and 
that it was a native or naturalized species. 
