ROSACEAE (ROSE FAMILY) 249 



the flowers white: calyx-tube campanulate, with short ovate lobes: follicles 5, 

 2-3 mm. long, glabrous or puberulent. S. betulaefolia. Through northern 

 Wyoming, Montana, and westward. 



2. Spiraea densiflpra Nutt. T. & G. Fl. N. A. 1: 414. 1840. Lower, rarely 

 more than 4 dm. high: stems usually decumbent and branching, especially 

 above: leaves elliptic, sharply serrate around the obtuse summit, glabrous, 

 2-4 cm. long: corymbs small, terminating the numerous branchlets, compact: 

 flowers rose-color: otherwise much like the preceding. S. betulaefolia rosea. 

 Subalpine; from the Teton Mountains, Wyoming, northwestward. 



8. PETROPHYTON Nutt. 



Stems very short, caespitose, woody. Leaves crowded-rosulate, entire, 

 without stipules. Flowering stems scapose, sparsely leafy-bracted. Flowers 

 perfect, in dense cylindrical simple or compound spikes. Disk free above, 

 nearly entire. Filaments distinct, rather longer than the spatulate-oblong 

 obscurely pubescent petals. Stigma simple; ovules 2-3; the seeds 1-2. 



1. Petrophyton caespitosum (Nutt.) Rydb. Mem. N. Y. Bot. Gard. 1: 206. 

 1900. Densely matted: leaves rosulate, about 1 cm. long, silky-villous : 

 scapes 5-20 cm. high: flowers white: calyx silky-villous, the segments ovate, 

 acute. On shelving exposed rocks in the mountains; northern Wyoming, 

 Montana, and westward. 



9. KELSEYA Rydb. 



Densely caespitose, the matted tuft consisting of the short freely branched 

 fascicled stems. Leaves closely imbricated the whole length of the branchlets, 

 long-persistent (only the outer ones remaining green). Flowers solitary at 

 the ends of the branchlets, on pedicels so short that they remain concealed 

 by the leaves that surround them. Calyx hirsute, the 5 oblong obtuse lobes 

 longer than its tube. Petals spatulate, twice as long as the calyx. Stamens 10, 

 equaling the petals, inserted on the margin of the entire wholly united disk. 

 Carpels 5, glabrous; the slender styles as long as the stamens; ovules pend- 

 ulous. Eriogynia Wats. Bot. Gaz. 15: 241. pi. 14. 1890. 



1. Kelseya uniflora (Wats.) Rydb. Mem. N. Y. Bot. Gard. 1: 207. 1900. 

 (Characters as given above.) (Eriogynia uniflora Wats. 1. c.) Big Horn 

 Mountains, Wyoming; also in Montana. 



10. CHAMAEBATIARIA Maxim. 



A stout diffusely branched glandular pubescent shrub. Leaves coriaceous, 

 small, bipinnately dissected, stipulate. Flowers in a leafy terminal racemose 

 panicle, perfect, white. Follicles coriaceous, 1-valved, connate at .base, sev- 

 eral-seeded. 



1. Chamaebatiaria millefolium (Torr.) Maxim. Act. Hort. Petrop. 6: 225. 

 1879. More or less tomentose: leaves narrowly lanceolate in outline, scattered 

 or fascicled at the ends of the branches, with very numerous (about 20) pinnae 

 and minute oblong obtuse leaflets (about 6 pairs) : the erect acute lobes of the 

 calyx nearly equaling the orbicular petals: carpels 5, pubescent. Western 

 Wyoming to California. 



11. ARUNCUS Adans. GOAT'S BEARD 



A large herb, with bi- or tri-ternately divided leaves. Flowers dioecious, 

 small, white, in numerous filiform panicled spikes. Calyx marcescent in fruit. 

 Stamens hypogynous. Carpels cartilaginous, 1-valved, distinct, few-seeded. 



1. Aruncus Sylvester Kost. Ind. Hort. Prag. 15. 1844. Smooth, branching, 

 7-15 dm. high: leaves large; leaflets thin, sparingly villous beneath, ovate to 



