118 ROSACEAE 



1. OPULASTER Medic. Nine-bark. 

 Carpels 3-5, united only at the base, turgid. 



Mature carpels glabrous, ovate, usually 5 ; leaves of the sterile shoots scarcely longer 



than broad. 1. O. capitatus. 



Mature carpels stellate, short-ellipsoid, abruptly acute, usually 3 or 4. 



Leaf-blades deeply lobed, as broad as long, cordate at the base; western species. 



2. O. cordatus. 

 Leaf-blades shallowly round-lobed, not cordate at the base, usually longer than 

 broad; eastern species. 3. U. intermedius. 



Carpels 2, united half theii length, or only 1 . 



Carpels usually 2; stamens similar or nearly so. 



Mature carpels more or less turgid; styles more or less spreading. 



Bracts obovate or spatulate, often foliaceous and more or less persistent. 



4. O. bracteatus. 

 Bracts linear or linear-oblanceolate, membranous and caducous. 



Pedicels and the hj-panthiimi almost glabrous; sepals stellate only on the 

 inner surface and near the margin ; shriib 1 m. high or more. 



5. O. glabratus. 

 Pedicels, hj-panthium and caly.x densely stellate; shrub 0..5 m. high or less. 



Leaves green on both sides, almost glabrous. 6. O. monogyTius. 



Leaves paler and densely stellate beneath. 7. O. Hapemanii. 



Mature carpels flattened and decidedly keeled; styles erect. 8. O. malraceus. 

 Carpels usually solitary; every other filament longer and with more dilated base; 

 leaves small, finely stellate. 9. O. allernans. 



2. SPIRAEA L. Meadow Sweet. 



Panicle flat-topped; sepals erect or merely spreading. 



Petals pink or rose-colored; corymb small. 1. S. densiflora. 



Petals white, seldom tinged with rose; corymb larger. 2. S. lucida. 



Panicle elongate, conical or ovoid, or lanceolate. 

 Sepals merely spreading; disk obsolete. 



Inflorescence glabrous; leaf-blades broadly oblanceolate to obovate. 



3. S. latifolia. 

 Inflorescence pubescent; leaf-blades narrowly oblanceolate. 4. S. alba. 



Sepals soon refle.xed; disk usually rather conspicuous. 

 Leaves not tomentose beneath. 



Stem glabrous; leaves serrate to near the base. 5. S. idahoensis. 



Stem more or less pubescent; leaves toothed above the middle. 



6. S. Menziesii. 

 Leaves tomentose beneath. 7. S.Douglasii. 



3. PETROPHYTUM (Nutt.) Rydb. 



Leaves spatulate, spreading; racemes short, 1-4 cm. long; bracts usually shorter than the 

 flowers. 1. P. caespitosum. 



Leaves narrowly oblanceolate, erect or ascending; inflorescence 4-10 cm. long, often 

 branched; bracts usually exceeding the flowers. 2. P. elatius. 



4. KELSEYA (S. Wats.) Rydb. l. K. uniflora. 



5. LUETKEA Bong. l. L. pectinata. 



6. ARUNCUS (L.) Adans. Goat's Beard. l. .4. acuminatus. 



7. CHAMAEBATIARIA (Porter) Maxim. Fern-bush. i. C. Millefolium. 



8. SERICOTHECA Raf. Ocean Spray, Mountain Spray. 



Leaves grajish- or whitish-tomentose and villous beneath. 



Inflorescence ample, well-compound; leaves usually over 3 cm. long. 



Leaf-blades abruptly contracted below, scarcely decurrent on the petioles, 4—10 



cm. long. 1. S. discolor. 



Leaf-blades cuneate at the base and distinctly decurrent on the winged petioles, 

 2-.5 cm. long. 2. S. dumosa. 



Inflorascence small and narrow, simple, racemose, or with a few short, spreading 

 branches; leaves usually less than 2 cm. long, finely pubescent and green above, 

 white silky-villous and tomentose beneath. 3. S. microphylla. 



Leaves glandular-atomiferous and sUghtly hairy on the veins beneath, not at all tomen- 

 tose, 1-1.5 cm. long, glabrous or sparingly pubescent. 4. S. glabrescens. 



9. HORKELIA Cham. & Schlecht. 



Plant less than 3 dm. high; petals 2-3 mm. long. 1. H. parviflora. 



Plant more than 3 dm. high; petals 3-6 mm. long. 



Leaflets ovate or oval, 2-3 cm. long; bracts generally exceeding the inflorescence. 



2. //. capitata. 

 Leaflets obovate or cuneate, usually less than 2 cm. long; bracts shorter than the 

 inflorescence. 3. H. fusca. 



10. IVESIA T. & G. 



Leaflets numerous, more or less crowded, usually divided to near the base. 



Stem leafy; stamens 20; claws of the wliite petals obsolete. 1. /. Kingii. 



