110 IOWA ACADEMY OF SCIENCES. 



soboliferia, Ammopldla longifoUa and Sporobolvs Hookerl, 

 S. brevifolius and an unnamed western species which has hereto- 

 fore beeti referied to S cuspidatus. I may also remark that a 

 peculiar thistle occurs, the Gnlcus altissimus, var. Jilil]jendulus. 



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 moi^tur8, ir, dries out quickly and the 

 roots easily peaetrate the toil to draw on the contained moist- 

 ure below. This certainly cannot be the reason, since the 

 luess extends along the river courses in the interior. Some 

 of thfse plants, since the cultivation of the soil, have shown 

 some tendency to spread, as in Euphorhia marginata, Lygodesmia 

 iuncea, Grmdelia squarrosa, which are tramping eastward to 

 menace the farmer. 



Were the seeds of some of these plants brought to Iowa 

 with 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 ATaximiliani, are not 

 uncommon, which shows that the woody area of southwestern 

 Iowa is in part a barrier against a farther eastern extension. 

 Bat why did the plants not extend beyond the very narrow 

 licaits, as the forest area does not encroach directly on the 

 loess mounds? I am at a loss to explain this most peculiar 

 disrribution. 



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, i) Dr. Miilspaugh 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 



