KOSACEAE (rose FAMILY) 249 



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

 2-3 mm. long, glabrous or jJuberulent. S. betulaefoUa. — Through northern 

 Wyoming, Montana, and westward. 



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

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

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

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

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

 Subalpiue; from the Teton Mountains, Wyoming, northwestward. 



& 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.J 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; Qorthem Wyoming, 

 Montana, and westward. < 



9. KELSEYA Rydb. 



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

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

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

 the ends of the braiichlets, on pedicels so short thit 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, 

 equaUng the petals, inserted on the margin of the entire whoUy united disk. 

 Carpels 5. glabrous; the slender styles as' long as the stamiens; ovules pend- 

 uloua.-^IIrio^nMi Wats. Bot. Gaz. 15: 241. pi. 14. 1890. 



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

 (Characters as given above.) (JEriogynia uniflora Wats. L 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 Beabd 



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

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

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



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

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



