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| 1 Petals blue, red, or pink (rarely white); capsule 5-10 mm long; [section Linum]. |
| ..2 Petals red or pink |
| ..2 Petals blue (rarely white). |
| ....3 Inner sepals with minutely ciliate margins; stigmas slender, elongate; capsule 6-10 mm long |
| ....3 Inner sepals entire; stigmas capitate; capsule 5-7 mm long. |
| ......4 Flowers heterostylous (some flowers with stigmas below the anthers, others with stigmas well above the anthers) |
| ......4 Flowers homostylous (flowers with stigmas at about the level to slightly above the anthers) |
| ........5 Perennials; styles 2-12 mm; capsule apices acute |
| ........5 Annuals; styles 1–3 mm; capsule apices obtuse |
| 1 Petals predominantly light to dark yellow (sometimes also with other coloration, including orange, copper, salmon, brown, and red bands or blotches); capsules 1-4 mm long; [section Linopsis]. |
| ..........6 Outer sepals entire (very rarely sparsely glandular-toothed), the inner sepals entire or sparsely to conspicuously glandular-toothed; leaves without red or brown stipular glands flanking the attachment to the stem. |
| ............ 7 Fruit as long as broad or longer, its apex acute, apiculate, or obtuse, (2-) 2.2-3.2 (-3.3) mm long; leaves mostly 1.3-4.3 mm wide. |
| ............ ..8 Leaves opposite; fruit subspherical, abruptly short-pointed |
| ............ ..8 Leaves all or mostly alternate (a few pairs of leaves at the base of the stem sometimes opposite); fruit ovoid to pyriform. |
| ............ ....9 Leaves (1.2-) 2.3-4.3 (-5.6) mm wide, mostly 25-50 below the inflorescence; septa of the fruit sparsely but conspicuously ciliate; false septa incomplete; fruit apex acute, the exposed portions purple |
| ............ ....9 Leaves (1.0-) 1.3-2.0 (-3.2) mm wide, mostly 50-165 below the inflorescence; septa of the fruit glabrous; false septa virtually complete; fruit apex rounded to apiculate, the exposed portions purple or yellow. |
| ............ ......10 Fruit 3.4-3.8 mm long, 3.2-3.4 mm in diameter |
| ............ ......10 Fruit (2.0-) 2.3-3.2 (-3.3) mm long, 1.7-3.1 mm in diameter. |
| ............ ........11 Fruit ovoid, (2.8-) 3.0-3.2 (-3.3) mm long, 2.5-3.1 mm in diameter, the apex minutely apiculate, the exposed portions yellow; seeds 2.1-2.4 mm long; anthers averaging 1.2 mm long |
............ ........11 Fruit pyriform, (2.0-) 2.3-2.8 (-3.0) mm long, 1.7-2.6 mm in diameter, the apex rounded, the exposed portions purple; seeds (1.6-) 1.7-2.0 (2.1) mm long; anthers averaging 0.8 mm long |
| ............ 7 Fruit broader than long, its apex depressed, flattened, or broadly rounded, (1.3-) 1.5-2.1 (-2.3) mm long; leaves mostly 1.9-9.3 mm wide. |
| ............ ..........12 Margins of the inner sepals with conspicuous stalked glands (these few or even absent in L. medium); mature fruits of dried specimens usually adhering to the plant. |
| ............ ............ 13 Leaves translucent, with minutely apiculate apices; inner sepals conspicuously glandular-toothed; [widespread in our region] |
| ............ ............ 13 Leaves opaque, with obtuse apices; inner sepals sparsely glandular-toothed (or entire); [questionably present in n. PA northwards] |
| ............ ..........12 Margins of the inner sepals glandless, or with a few inconspicuous, sessile glands; mature fruits of dried specimens usually shattering and falling freely. |
| ............ ............ ..14 Styles distinct (free); [collectively widespread in our region]. |
| ............ ............ ....15 Inflorescence paniculate, the lower inflorescence branches not elongate, their tips not nearly reaching the tips of the upper inflorescence branches; branchlets striate-ridged; leaves mostly opposite (usually to beyond the midpoint from the base of the plant to the first inflorescence branch) |
| ............ ............ ....15 Inflorescence corymbose, some (at least) of the lower branches of the inflorescence elongate, their tips nearly equaling the tips of the upper inflorescence branches; branchlets terete or nearly so; leaves mostly alternate (usually the opposite leaves of the lower stem not extending beyond the midpoint from the base of the plant to the first inflorescence branch) |
| ............ ............ ..14 Styles connate (united basally); [west of the Mississippi River, in LA, OK, and TX]. |
| ............ ............ ......16 Distal leaves and bracts not ciliate; capsule false septa entirely hyaline, or with cartilaginous portion very narrow, uniform, distal |
| ............ ............ ......16 Distal leaves and bracts sparsely ciliate; capsule false septa with cartilaginous portion conspicuously broader near base |
| ..........6 Inner and outer sepals all very conspicuously glandular-toothed; leaves with 2 red or brown stipular glands flanking the attachment to the stem (these absent or obscure in L. smallii and L. rigidum var. rigidum – but check leaves on the upper and lower stem). |
| ............ ............ ........17 Styles distinct (free). |
| ............ ............ ..........18 Styles 2-3 mm long; petals 4-6.5 mm long; [s. FL] |
| ............ ............ ..........18 Styles 3-6.5 mm long; petals 7-11 mm long; [TX] |
| ............ ............ ........17 Styles connate (united) basally or through most of their length. |
| ............ ............ ............ 19 Capsules dehiscing into 10, 1-seeded segments; sepals persistent. |
| ............ ............ ............ ..20 Sepals 2.3-3.5 mm long, acute; inflorescence consisting of 1 or more elongate and racemiform branches; dried plants dark, purple-dotted; [Coastal Plain of FL Panhandle] |
| ............ ............ ............ ..20 Sepals (3.1-) 3.6-5 (-7.3) mm long, acuminate; inflorescence an open panicle; dried plants pale green; [widespread, mainly inland provinces except westwards] |
| ............ ............ ............ 19 Capsules dehiscing into 5, 2-seeded segments; sepals persistent or not. |
| ............ ............ ............ ....21 Outer sepals ovate or obovate, margins undulate or crenate, with sessile gland near summit of each crenation |
| ............ ............ ............ ....21 Outer sepals linear, linear-lanceolate, lanceolate, or narrowly ovate, margins glandular-toothed. |
| ............ ............ ............ ......22 Styles 6-9.5 mm long. |
| ............ ............ ............ ........23 Petals with prominent wine-colored band below their midpoints |
| ............ ............ ............ ........23 Petals reddish below middle. |
| ............ ............ ............ ..........24 Sepals green; stigmas green; capsules relatively thick-walled and opaques |
| ............ ............ ............ ..........24 Sepals grayish or purplish; stigmas dark gray; capsules relatively thin-walled and translucent |
| ............ ............ ............ ......22 Styles 2-6 mm long. |
| ............ ............ ............ ............ 25 Sepals short-awned; [peninsular FL]. |
| ............ ............ ............ ............ ..26 Stem puberulent or scabrous on the angles throughout; plants (11-) 17-28 (-33) cm tall; petals 9-11 mm long; styles 4.4-6.1 mm long; stipular glands present |
| ............ ............ ............ ............ ..26 Stem glabrous (or sometimes sparsely puberulent or scabrous near the base); plants (17-) 28-45 (-64) cm tall; petals 11.5-17 mm long; styles 5.1-9.1 mm long; stipular glands usually absent or essentially so |
| ............ ............ ............ ............ 25 Sepals acute to acuminate; [OK,TX] |
| ............ ............ ............ ............ ....27 Stamens 4-5 mm long |
| ............ ............ ............ ............ ....27 Stamens 6-8 mm long |