I. Ovary superior and not enclosed in the calyx tube at maturity.
[*] Calyx deciduous, without bractlets, pistil solitary, becoming a drupe.
Tribe I. PRUNEÆ. Trees or shrubs, with simple mostly serrate leaves. Ovules 2, pendulous, but seed almost always solitary. Style terminal.
1. Prunus. Flowers perfect. Lobes of calyx and corolla 5. Stone of the drupe bony.
[*][*] Calyx mostly persistent; pistils few to many (rarely solitary).
[+] Calyx without bractlets; ovules 2--many.
Tribe II. SPIRÆEÆ. Pistils mostly 5, becoming 2--several seeded follicles. Shrubs or perennial herbs.
[a.] Calyx short, 5 cleft. Petals obovate, equal.
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.
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.