30 NORTH AMERICAN FAUNA [No. 55 



Dodecatheon tetrandrum, Angelica lyallii, Saxifraga mertensiana, 

 Rhodiola frigida, Polygonum imbricatum, Pedicularis l>racteosa and 

 racemosa, Ranunculus populago, Pentstemon fruticosus, and Aster 

 integrifolius and cusickii. 



In the Steens Mountains the Hudsonian Zone is poorly denned, 

 owing to the aridity of the summits, absence of trees and shrubby 

 growth, and greatly denuded and eroded slopes. Still there is suffi- 

 cient native life to serve as an approximate guide to the zonal divi- 

 sions. The principal Hudsonian indicators in plants are dwarf 

 willows, alpine juniper (Juniperus sibirica), thorny gooseberry, red 

 currants, shrubby cinquefoil (D^asiphora frutioosa) , dwarf blueberry 

 (V actinium scoparium), Kalmia glauca microphylla, Artemisia tile- 

 sii, Eriogonum umbellatum and vweum, Saseifraga colunibiana, 

 Sytmphoricarpos acutios, Spraguea multiceps, PolygonUm bistor- 

 toides, Phacelia sericea, Quamasia leichtlinii, Dodecatheon puberu- 

 Iwrn, Pedicularis surrecta, Helenium hoopesii, Phlewn alpinwni, and 

 Delphinium cyanoreios. 



ARCTIC-ALPINE ZONE 



Arctic- Alpine, the last belt of dwarf plant and scanty animal life, 

 corresponding to the Arctic tundra of the far north, is represented 

 on most of the peaks in Oregon reaching above 9,000 feet in altitude. 

 On Mount Hood it ranges from about 6,000 feet on northeast and 

 7,000 feet on southwest slopes upward to the permanent ice and snow, 

 which cover most of the higher parts of the peak ; and on Jefferson 

 from 6,500 and 7,500 feet upward. On the Three Sisters the zone 

 lies above 7,000 and 8,000 feet, respectively, on the cold and warm 

 slopes; on Mount McLoughlin (Pitt), above 8,000; in the Blue 

 Mountains and Steens Mountains, above 8,000 and 9,000 feet, varying 

 somewhat in accordance with varying local conditions of slope, soil, 

 wind, and moisture, running 1 lower on steep northerly slopes where 

 the sun's rays are partially cut off and higher on the steep southerly 

 slopes which catch the more nearly vertical rays of the sun. The 

 effect of high and low base level is still apparent in this highest of 

 the life zones. 



PLANTS 



In the Arctic- Alpine Zone of the Cascade peaks are such low or 

 prostrate plants as Ranunculus eschscholtzii. Anemone hudsoniana, 

 Antennaria media. Phlox douglasii and diffusa, Pentstemon menziesii, 

 Veronica alpina, Silene suksdorfi, Saodfrag tolmiei and bongardi, 

 Potentilla flab elli folia, Oxyria digyna, Polygonwn newberryi, Genti- 

 ana calycosa, Lewisia columbiana, Epilo'bium alpinum and anagalli- 

 di folium, Erigeron salsuginosus, Hieracium gracile, Oreastrum 

 alpigaenum. 



Arctic- Alpine Zone in the Blue Mountains is marked by such dwarf 

 vegetation as the dwarf willow (Salix nivalis), Dry as octopetala, 

 Ivesia gordoni, Sieversia rossii, Potentilla flabe7tifolia, Sawifraga 

 deMlis and ~bongardi, Silene acaulis, Phlox diffusa and douglasii, 

 Arenaria vema, sajanensis and nuttallii, Claytonia megarrhiza, Epi- 

 lobium, alpinum and anagallidifolium, Lewisia nevadensis and tri- 

 phylla, Dodecatheon jeffreyi, Oxyria digyna, Eriogonum piperi,, 



