110 
IOWA ACADEMY OP SCIENCES. 
soMiferia, Ammophila longifolia and Sporobolus Eoolceri, 
8. brevifolius and an unnamed western species which has hereto- 
fore been referred to S. cuspidatus. I may also remark that a 
peculiar thistle occurs, the Gnicus altissimus, ynx. Jililpendulus. 
Why is it; that these peculiar hiJls, not more than a few 
hundred feet wide, should have such a local western flora? 
The soil is retentive of moisture, it dries out quickly and the 
roots easily penetrate the soil to draw on the contained moist- 
ure below. This certainly cannot be the reason, since the 
loess extends along the river courses in the interior. Some 
of these plants, since the cultivation of the soil, have shown 
some tendency to spread, as in Euphorbia marginata^ Lygodesmia 
juncea^ Grindelia squarrosa^ which are tramping eastward to 
menace the farmer. 
Were the seeds of some of these plants brought to Iowa 
tvith the buffalo, as has been suggested for buffalo grass? 
Some of the plants are disseminated by the wind, and in others 
the water can by a purely mechanical means bring them to the 
base of the mound. With the more woody country of south- 
eastern Iowa there seems to have been but little chance for 
these plants to spread beyond the bluffs. In northwestern 
Iowa some of these plants, like Helianthus Maximiliani, are not 
uncommon, which shows that the woody area of southwestern 
Iowa is in part a barrier against a further eastern extension. 
But why did the plants not extend beyond the very narrow 
limits, as the forest area does not encroach directly on the 
loess mounds? I am at a loss to explain this most peculiar 
distribution. 
In the list appended I enumerate the most striking plants. 
The writer is under obligations to Mrs. Rose Schuster Taylor 
and Miss Bandusia Wakefield, of Sioux City, for favors 
rendered; also Mr. E. D. Ball, of Little Rock; Mr. W. Newell 
and J. Jensen, of Hull, and E. G. Preston, of Battle Creek, 
for specimens, to Dr. Millspaugh for naming the Euphorbias. 
My own collections were made at various times near Sioux 
City, Hawarden, Onawa, Turin, Missouri Valley, Council Bluffs 
and Logan. The list could have been extended and localities 
added, but college material is not readily accessible at this 
time of the year. Miss Wakefield’s list is based on colored 
sketches in her possession. I have abbreviated all specimens 
credited to her as (B. W.), and those collected by myself as 
(L. H. P.). I have followed Gray’s Manual in arrangement of 
