66 IOWA ACADEMY OF SCIENCES. 



The Wjiethia aiiiplexicaiilis covers large areas in the open 

 parks between the Pinus M/irr(f//((Ha woods, with several 

 species of Aster and Erigeron. A species of Ilelicmfhus 

 and Arcnaria Fendleri, Potent ilia r/landiilosa, Erigeron gla- 

 bellus, and Achillea millefoliion are all abundant, either in 

 woods or in open places. 



At S,50U feet the glaciated area begins- The Salix mes- 

 ophytic area continues with smaller xerophytic parks. 

 The second flood plain contains arid belts, the chief plant 

 being Artemisia tridentata and a species of Bigelocia, broken 

 up, however, by small watered canons. The shores con- 

 tain not only mesophytic plants, like Populus fi-euniloides^ 

 and Salix pellifa. but a good growth of hydrophytes in the 

 bogs. Conifers like Abies siibalpina and Pinus MiiJ-rayana 

 are increasingly abundant. The upper zones are no longer 

 recognizable. They are cut up with small canons, and 

 numerous small lakes, many of the latter without an out- 

 let. • Three trees ara common here, Populus treinuloides, 

 Abies subalpina and Pinus Murragcoia. 



Just above the junction of east and west Black's Fork, 

 at an altitude of 9,200 feet, both streams have cut through 

 a glaciated debris of 100-150 feet; the benches are 

 extremely dry except where small streams have cut 

 through. The vegetation of the benches is xerophytic. as 

 well as the moraines. The first flood plain is essen- 

 tially mesophytic, abounding in willows, like Salix c/iloro- 

 vhtjlla, S. ntacrocarpum, TJialictnone alpinuni and Betula 

 glandulosus, but there are small xerophytic openings. The 

 soil of these areas consists of coarse sand, with a little 

 humus on the surface. 



Artemesia tridentata is the most characteristic plant, 

 with large, spreading mats of Arctosfaplujlos Uia-ursi, a 

 few Berberis repens and such herbaceous plants as Eriogo- 

 lunn umbellatunu Arenaria Fendleri^ Castilleia miniata, 

 Achillea Millefolimn, Campanula rotundifolia and Frasera 

 speciosa; of the trees an occasional Pinus Murrayana and 

 Populus treuiuloides occur. Both of these species, however, 

 occupy the depressions where water is more easily acces- 

 sible. 



