Lobelia sect. Stenotium (Presl, 1836) Lammers

Gutiérrez-Sánchez, Rosa Ivonne, Castro-Castro, Arturo, Gallegos, Jesús Guadalupe González-, López-Enríquez, Irma Lorena & Frías-Castro, Alfredo, 2018, Synopsis of the spurred species of Lobelia section Stenotium (Campanulaceae) in Sierra Madre Occidental, Mexico, and the description of two new species, Phytotaxa 338 (1), pp. 33-48 : 35

Key to the spurred species of Lobelia sect. Stenotium in Sierra Madre Occidental, Mexico (modified from Ayers 1987, 1990)

1. Decumbent or procumbent perennials spreading by underground rhizomes; pedicels erect and stationary during fruit maturation; corollas pink-purple .......................................................................................................................................................................... 2

- Erect annuals or taprooted perennials; capsules re-oriented during fruit maturation by movement of the pedicel; corollas blue, pale lavender, or white, rarely pink-purple .............................................................................................................................................. 5

2. Flowers in a terminal pedunculate raceme; spur extending 5–8 mm beyond ovary ............................................... L. macrocentron

- Flowers solitary or racemose in axils of foliaceous bracts; spur extending less than 4 mm beyond ovary ..................................... 3

3. Stems decumbent, simple, arising from well-developed rhizomes; leaves narrowly ovate to lanceolate; spur cylindrical ............... ........................................................................................................................................................................................ L. mcvaughii

- Stems procumbent, branching aboveground; leaves orbicular to widely ovate; spur conic ............................................................ 4

4. Leaves 3–6(–8) mm long ; flowers 0.9–1.1(–1.4) cm long including hypanthium; spur (5–) 7–10 mm long (measured from base of the upper calyx lobes); staminal tube 6–7 mm long; from Chihuahua .......................................................................... L. knoblochii

- Leaves (2–)4–14(–17) mm long ; flowers 1.2–1.6 cm long including hypanthium; spur 2–3 mm long (measured from base of the upper calyx lobes); staminal tube 2.4–6.6 mm long; from Durango ............................................................................... L. saturnini

5. Leaves linear to linear-lanceolate ..................................................................................................................................... L. flexuosa

- Leaves elliptic, ovate, reniform or cordate ....................................................................................................................................... 6

6. Flowers 9–11 mm long; spur more than 4 mm long ...................................................................................................... L. goldmanii

- Flowers 4–7 mm long; spur less than 2.5 mm long .......................................................................................................................... 7

7. Leaves mostly basal, the blades ovate, the margins repand-dentate ................................................................................................ 8

- Leaves all cauline, the blades entire, palmately-lobed or pinnatipartite, reniform or cordate, the margins dentate or incised, becoming laciniate above ............................................................................................................................................................................ 9

8. Inflorescence racemose with 10–15 flowers, flowers 6.5–7 mm long including hypanthium, cylindrical spur 2–2.5 mm long from the base of the upper calyx segments, staminal tube 4–4.5 mm long; from Chihuahua ................................................. L. endlichii

- Inflorescence racemose to paniculate, with (4–)10–35(–191), flowers 4–6 mm long including hypanthium, conical spur 0.5–1 mm long from the base of the upper calyx segments, staminal tube 1.3–2.5 mm long; from Nayarit ................................. L. rzedowskii

9. Leaves deeply pinnatipartite; from Durango and Sinaloa ................................................................................................ L. ayersiae

- Leaves entire or palmately-lobed; from western slopes of the Sierra Madre Occidental and Sierra Madre del Sur from Sonora, Mexico, to volcanic slopes in Costa Rica....................................................................................................................... L. cordifolia