Bacillares

Rojas-Martínez, Cecilia, Flores-Olvera, María Hilda, Ochoterena, Helga & Delgado-Salinas, Alfonso, 2019, An outstanding new species of Senna (Fabaceae: Caesalpinioideae) from southern Puebla, Mexico, Phytotaxa 405 (3), pp. 113-120 : 118

Key to the Mexican species of Series Bacillares , morphologically similar with Senna acatlanensis

1. Shrubs free standing, with virgate branches, less than 2 m tall; flowers 5–6 cm in diameter; petals bright yellow not fading as they dry-out, androecium with 4 abaxial staminodes, and 7–10 functional stamens; fruits 7.5–10 cm, with smooth, pubescent valves and sutures.................................................................................................................................................................... Senna acatlanensis

- Shrubs, sometimes with an scandent habit or trees, 2–15 m tall; flowers up to 3 cm in diameter; petals yellow fading dusty red as they dry-out; androecium with 3 abaxial staminodes, and 4–7 functional stamens; fruits 10–50 cm, with smooth or granular-papillate valves..................................................................................................................................................................................2.

2. Flower androecium with 4 functional stamens, other 3 suppressed; fruits up to 26 cm, compressed, with smooth valves ................ ................................................................................................................................................................................... Senna hayesiana

- Flower androecium with 7 functional stamens; fruits up to 50 cm, sub cylindrical, with smooth or granular-papillate valves.....................................................................................................................................................................................................................3.

3. Leaves with dark patches on above surface; stipules lanceolate and curved, with one vein, excentric; two stipitate, lanceolateovoid glands, one between each pair of leaflets; stamens with straight anthers; fruit 10–30 cm; with smooth valves; seeds faintly areolate ............................................................................................................................................................. Senna quinquangulata

- Leaves bicolored, above surface darker green without dark patches, stipules linear-lanceolate, 3-veined; with one sessile, ovoid or pyriform gland, between the proximal pair of leaflets; stamens with curved anthers; fruit 10–50 cm; with smooth or papillate valves; seeds exareolate or areolate...................................................................................................................................................4.

4. Flowering branches cylindrical, with a zigzag pattern; flower ovary with up to 100 ovules; fruits up to 24 cm, brilliant red to brownish coloured at maturity, with smooth valves; seeds areolate ........................................................................... Senna fruticosa

- Flowering branches cylindrical to shortly angulate, without a zigzag pattern; flower ovary with up to 250 ovules; fruits up to 50 cm, reddish-brown, with dense granular-papillate valves; seed exareolate ............................................................... Senna papillosa