136 



American Midland Naturalist Monograph No. 4 



tips, finely silky-hairy, forming basal rosettes at base of flowering stems; 



flowers small, white, borne in cylindric clusters ^2 to ly2 inches long on 



erect silky stems 2i/2 to 6 inches high. The plant from Sequoia, with less 



hairy stems and leaves, is sometimes designated as P. acuminatum Rydb. The 



sepals have longer pointed tips. (Syn. Spiraea caespitosa Nutt.). 



Occurrence. — sequoia, rare, on east side of the Great Western Divide: Big Arroyo. 

 ZION. GRAND CANYON. South Rim: Grand Canyon Village, 6,870 feet. Canyon, on 

 north side of Colorado River: Kaibab trail above Roaring Springs. 



Mountain Dryad (Dryas L.) 



The mountain dryads are dwarf creeping shrubs with their stems trailing 

 over rocks. White mountain dryad is found usually in high mountain passes 

 where it often forms large, dense, cushion-like mats. The yellow mountain 

 dryad occurs on high rocky talus slopes or along rocky river bars in the lower 

 valleys at Glacier National Park. The flowers of the former are white with 

 spreading petals, while those of the latter are yellow with erect petals. The 

 leaves are very much alike in the two species, but are very different from those 

 of any other plants found growing in areas where mountain dryads occur. 

 They are dark green above, densely white-felty below, with prominent indented 

 or sunken veins, the margins inrolled, with rounded teeth. During the late 

 summer the plants are conspicuous because of the fluffy white or tawny fruit- 

 ing heads borne on erect stems. 



Field Guide to the Species 



Petals white, spreading; sepals mostly Imear or narrowly oblong to lance-shaped; 



flower stems becoming 2 to 6 inches long in fruit I. D. ociopetala. 



Petals yellow, erect to form a cup-like flower; sepals mostly broadly lance-shaped to 



egg-shaped; flower stems becommg 6 to 10 inches long in fruit 



2. D. Drummond'i. 



1. Mount Washington Dryad (Dryas 

 octopetala L.), fig. 72. — -Leaf -blades mostly 

 rounded or somewhat heart-shaped at base; 

 flowers white, sometimes drying light yellowish 

 or cream-color, about % to 1 inch across, the 

 petals spreading; sepals usually narrowly lance- 

 shaped to linear, these and the cup below often 

 sparingly black-hairy; flower stems single- 

 flowered, 1/4 to 2 inches long, becoming li^ to 

 4 inches long in fruit. 



Occurrence. — mount rainier, rare, 7,000 to 

 8,500 feet. GLACIER, common, 7,000 feet and above: 

 Mount Altyn; Swiftcurrent Pass; trail to Swiftcur- 

 renl lookout; Piegan Pass; Hidden Lake Pass; Cut- 

 bank Pass; Triple Divide Pass; near Gunsight 

 Pass; Ahem Pass. YELLOWSTONE, common: 

 Mt. Holmes; Electric Peak; Beartooth Mountains. 

 GRAND TETON : tableland at head of Death Canyon, 

 9,800 feet. ROCKY MOUNTAIN, common above tim- 

 berline ; Long's Peak, 1 1 ,000 feet. 



Fig. 72. Mount Washington 



dryad (Dr^as 



octopetala) . 



