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| 1 Ovary inferior; fruit indehiscent (pome); [tribe Pyreae]. |
| ..2 Upper surface of leaves bearing dark glandular trichomes along the midrib (most easily seen with a 10× hand lens); shrubs |
| ..2 Upper surface of leaves lacking dark glandular trichomes along the midrib; shrubs and trees. |
| ....3 Ovary and fruit 10-locular; inflorescence a raceme (rarely a fascicle); pome < 1 cm in diameter |
| ....3 Ovary and fruit 5-locular; inflorescence a cyme, umbel, or fascicle (lacking an elongated central axis); pome 0.7-10 cm in diameter. |
| ......4 Styles distinct; exocarps (carpels within pericarp) bony and seedlike; trees and shrubs, with thorns |
| ......4 Styles usually connate at base; exocarps leather or papery and easily opened to expose seeds; small trees, unarmed, or armed with sharp spur branches. |
........5 Pome globose to ovoid, lacking stone cells; anthers yellow to white; styles connate at the base; leaves blunt to acuminate; [apples and crabapples] |
| ........5 Pome globose or pyriform, with stone cells; anthers reddish; styles distinct; leaves acute to acuminate; [pears] |
| 1 Ovary superior; fruit dehiscent (aggregate of follicles, or capsule) or indehiscent (drupe, aggregate of drupelets, aggregate of achenes). |
| ..........6 Leaves opposite; fruit a drupe; [tribe Kerrieae] |
| ..........6 Leaves alternate; fruit various (see below). |
| ............ 7 Leaves large, > 10 cm wide, palmately veined, palmately lobed; fruit an aggregate of drupelets; [tribe Rubeae] |
| ............ 7 Leaves smaller, < 8 cm wide, pinnately veined, either not lobed or basally pinnately lobed; fruit a drupe, a capsule, an aggregate of follicles, or an aggregate of achenes. |
| ............ ..8 Leaves singly serrate or entire, not lobed basally. |
| ............ ....9 Gynoecium of separate carpels; fruit an aggregate of follicles; [tribe Spiraeeae] |
| ............ ....9 Gynoecium of fused carpels; fruit either a fleshy drupe or a capsule. |
| ............ ......10 Ovary 5-angled in ×-section; fruit a 5-angled capsule; leaves obovate, obviously broadest towards the tip; [tribe Osmaronieae] |
| ............ ......10 Ovary circular in ×-section; fruit a fleshy spherical drupe; leaves generally broadest near or below the middle; [tribe Amygdaleae] |
| ............ ..8 Leaves doubly serrate, also often lobed towards the base. |
| ............ ........11 Corolla yellow; stems arching, green; fruit an aggregate of drupe-like achenes (dry and indehiscent); [tribe Kerrieae] |
| ............ ........11 Corolla white to pink or rose; stems not both arching and green; fruit various (see below). |
| ............ ..........12 Inflorescence a dense, umbel-like corymb; leaf apices rounded to acute; fruit an aggregate of 5 follicles; [tribe Neillieae] |
| ............ ..........12 Inflorescence a raceme or a leafy panicle; leaf apices acuminate. |
| ............ ............ 13 Fruit a single follicle; [alien, planted, and rarely naturalized, as in e. VA]; [tribe Neillieae] |
| ............ ............ 13 Fruit an aggregate of 2-4 drupe-like achenes; [rare native of calcareous habitats in sc. TN, nw. GA, n. AL, and disjunct westward in AR and MO]; [tribe Kerrieae] |