2. Spiræa. Flowers perfect or diœcious. Pods 1-valved. Herbs or shrubs; leaves simple or pinnate. 3. Physocarpus. Pods inflated, 2-valved. Shrub; leaves palmately lobed. [b.] Calyx elongated, 5-toothed. Petals slender, unequal. 4. Gillenia. Herbs; leaves 3-foliolate. Tribe III. RUBEÆ. Pistils several or numerous, becoming drupelets in fruit. Ovules 2 and pendulous, but seed solitary. Perennials, herbaceous or with biennial soft-woody stems. 5. Rubus. Pistils numerous, fleshy in fruit, crowded upon a spongy receptacle. 6. Dalibarda. Pistils 5--10 in the bottom of the calyx, nearly dry in fruit. [+][+] Calyx lobes mostly with bractlets; ovule solitary. Tribe IV. POTENTILLEÆ. Pistils few--many, 1-ovuled, becoming dry achenes. Herbs. [a.] Styles persistent and elongated after anthesis, often plumose or jointed. 7. Geum. Calyx lobes usually with 5 alternating small bractlets. Stamens and carpels numerous, styles becoming plumose or hairy tails, or naked and straight or jointed. [b.] Styles not elongated after anthesis, mostly deciduous. 8. Waldsteinia. Petals and calyx lobes 5; small or no bractlets. Stamens numerous. Achenes 2--6; styles deciduous from the base. 9. Fragaria. Flower as in Potentilla. Receptacle much enlarged and pulpy in fruit. 10. Potentilla. Petals 5 (rarely 4) conspicuous. Calyx lobes as many, with an alternating set of bractlets. Stamens and achenes numerous; the latter heaped on a dry receptacle. Styles commonly more or less lateral, deciduous or not enlarging in fruit. 11. Sibbaldia. Petals minute; stamens and achenes 5--10; otherwise as Potentilla. II. Ovaries inferior or enclosed in the calyx-tube. Tribe V. POTERIEÆ. Pistils 1--4, becoming achenes, completely enclosed in the dry and firm calyx-tube, which is constricted or nearly closed at the throat. Herbs with compound or lobed leaves. Petals often none. 12. Alchemilla. Calyx urceolate, bracteolate. Petals none. Stamens 1--4. Flowers minute, clustered. 13. Agrimonia. Calyx turbinate, with a margin of hooked prickles. Stamens 5--12. Flowers yellow, in long racemes. 14. Poterium. Calyx lobes petaloid; tube 4-angled, naked. Petals none. Flowers densely capitate or spicate. Tribe VI. ROSEÆ. Pistils many, becoming bony achenes, enclosed in the globose or urn-shaped fleshy calyx-tube, which resembles a pome. Petals conspicuous. Stamens numerous. 15. Rosa. The only genus. Prickly shrubs with pinnate leaves. Tribe VII. POMEÆ. Carpels 2--5, enclosed in and coalescent with the fleshy or berry-like calyx, in fruit becoming a 2--several-celled pome. Trees or shrubs, with stipules free from the petiole. [a.] Cells of the compound ovary as many as the styles (2--5), each 2- (rarely several-) ovuled. 16. Pyrus. Pome containing 2--5 papery or cartilaginous carpels. 17. Cratægus. Pome drupe-like, with 1--5 bony stones or kernels. Usually thorny. [b.] Cells of the compound ovary becoming twice as many as the styles, each 1-ovuled.