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| 1 Inflorescence a spike or panicle of spikes; plants from corms; flowers slightly zygomorphic. |
| ..2 Stem usually branched, the inflorescence appearing paniculate; tepals orange to red |
| ..2 Stem unbranched, the inflorescence a spike; tepals any of a wide range of colors (including orange and red) |
| ....3 Inflorescence bent at its base, the inflorescence axis more-or-less horizontal, the flowers facing upward |
| ....3 Inflorescence erect, the flowers facing outward |
| 1 Inflorescence an umbellate 1-sided cyme; plants from rhizomes or bulbs; flowers actinomorphic. |
| ......4 Leaves planar; plants from rhizomes (or indistinct) or a bulb (in Iris xiphium). |
| ........5 Style branches broad, petaloid, terminating in paired crests |
| ........5 Style branches not broad or petaloid. |
| ..........6 Tepals 16-35 mm long, orange or red; seeds 4-6 mm in diameter |
..........6 Tepals 6-15 mm long, blue, purple, lavender, pink, magenta, white, or yellowish-white; seeds 0.6-1.3 mm in diameter |
| ......4 Leaves plicate; plants from bulbs. |
| ............ 7 Tepals unequal, the inner whorl < ½ as long as the outer whorl |
| ............ 7 Tepals nearly equal in length. |
| ............ ..8 Style recurved, with 3 flat branches that are < 2 mm long |
| ............ ..8 Style straight, each of the 3 branches further divided into slender lobes |
| ............ ....9 Style branches divided for ca. ½ their length; style arms arching over or between the anthers; tepals dark purple |
| ............ ....9 Style branches divided nearly to base; style arms extending horizontally between the anthers; tepals blue, white in the center |