Louteridium

Daniel, Thomas F. & Tripp, Erin A., 2018, Louteridium (Acanthaceae: Acanthoideae: Ruellieae: Trichantherinae): Taxonomy, Phylogeny, Reproductive Biology, and Conservation, Proceedings of the California Academy of Sciences 65 (2), pp. 41-106 : 69-70

Key to Species of Louteridium

1a. Stamens 4; leaves ± clustered on stems, seasonally deciduous (i.e., plants leafless for part of the year); occurring in dry, deciduous or subdeciduous forests............... Sect. Tetrandrium

2a. Calyx 5–9 mm long, lobes 3.5– 4.8 mm long, posterior lobe broadly ovate to subtriangular; Guerrero .................................................. L. rzedowskianum

2b. Calyx 10–32 mm long, lobes 7. 5–32 mm long, posterior lobe linear to lanceolate to ovate to subelliptic to subrhombic-obovate.

3a. Dendritic trichomes present on vegetative and reproductive structures; inflorescence a raceme (i.e., dichasia sessile); Oaxaca ........................ L. dendropilosum 3b. Dendritic trichomes absent on vegetative and reproductive structures; inflorescence usually a thyrse (i.e., dichasia usually pedunculate); western Mexico (Jalisco and

Michoacán) or Belize.

4a. Calyx 10–16 mm long, lobes 7. 5–12 mm long; corolla externally pubescent with glandular and eglandular trichomes; inflorescence rachis pubescence including glandular trichomes; capsule 32–42 mm long, pubescent with eglandular and glandular trichomes; style 75–77 mm long; seeds 16–24 per capsule; Michoacán ....

....................................................... L. brevicalyx

4b. Calyx 17–28 mm long, lobes 15–37 mm long; corolla externally glabrous; inflorescence rachis glabrous or pubescent with eglandular trichomes only; capsule

(20–) 23–30 mm long, glabrous or pubescent with eglandular trichomes only; style

50–67 mm long; seeds up to 16 per capsule.

5a. Inflorescence rachis, peduncles, and pedicels glabrous; calyx lobes linear to lance-linear, 3–5 mm wide; corolla 35–40 mm long; stamens 55–77 mm long, thecae 6.5–9. 5 mm long; capsules glabrous; Belize......... L. chartaceum 5b. Inflorescence rachis, peduncles, and pedicels pubescent with eglandular trichomes; calyx lobes ovate-elliptic to elliptic to obovate, 9–15 mm wide; corolla 50–55 mm long; stamens 72–90 mm long, thecae 10–12 mm long; capsules pubescent; western Mexico (Jalisco and Michoacán)..... L. koelzii

1b. Stamens 2; leaves ± evenly distributed along young stems, not all seasonally deciduous (i.e., plants never entirely leafless); occurring in moist to wet forests...................................................................... Sects. Louteridium and Parcostamium

6a. Leaf blades oblanceolate to obovate; inflorescence appearing conspicuously dichotomously branched; bracteoles of a pair connate along one side for up to 1/2 their length and subsaccate at base; posterior lobe of calyx subsaccate or with a flap-like appendage at base; corolla externally glabrous; capsule glabrous; Mexico...................... L. parayi

6b. Leaf blades cordate to ovate to broadly ovate to elliptic to broadly elliptic to obovate; inflorescence not appearing dichotomously branched; bracteoles neither connate nor subsaccate; posterior lobe of calyx not subsaccate/appendaged at base; corolla externally pubescent; capsule pubescent (glabrous in L. costaricense ); Mexico and Central America.

7a. Bracts persistent during flowering; capsule glabrous, stipe 7–12 mm long; southern Central America ( Costa Rica and Panama)....................... L. costaricense 7b. Bracts caducous during flowering (or sometimes proximal bracts persisting in L. donnell-smithii ); capsule with sessile or stipitate glands, stipe 1–4 mm long; Mexico and northern Central America.

8a. Leaves subsucculent; posterior calyx lobe planar; style 48–73 mm long, seeds up to 20 per capsule; northeastern Mexico (Tamaulipas).......... L. tamaulipense 8b. Leaves membranaceous; posterior calyx lobe conduplicate; style 72–92 mm long; seeds up to 16 per capsule; southern Mexico, Belize, Guatemala, and western Honduras............................................... Sect. Louteridium

9a. Young stems and leaves densely pubescent with erect to flexuose eglandular trichomes to 2 mm long; inflorescence peduncles and rachis, flower pedicels, and abaxial surface of calyx pubescent with glandular and eglandular trichomes to 2.8 mm long (viscid); leaf margin crenate-dentate.......................................................... L. donnell-smithii 9b. Young stems and leaves glabrous or pubescent with erect, flexuose, retrorse, or antrorse eglandular trichomes <0.05– 0.5 mm long; inflorescence peduncle and rachis, flower pedicels, and abaxial surface of calyx glabrous or pubescent with eglandular trichomes <0.05–1 mm long; leaf margin entire to crenate (sometimes to crenate-dentate in L. mexicanum ).

10a. Rachis glabrous or pubescent with flexuose to flexuose-antrorse trichomes 0.2– 1 mm long (villous); pedicels glabrous or villous; abaxial surface of calyx either appearing glabrous (although covered with glandular punctations ˂ 0.05 mm in diameter) or villous along keel; capsule sparsely puberulent with sessile to subsessile glands to 0.05 mm long; leaf blades broadly ovate to ovate to elliptic to broadly elliptic; Gulf of Mexico and Caribbean Sea versants.................. L. mexicanum 10b. Rachis puberulent with (retrorse to) erect to flexuose to antrorse trichomes to 0.05 mm long; pedicels puberulent with erect to retrorse (to antrorse) trichomes to 0.05 mm long; abaxial surface of calyx pubescent like pedicels and sometimes with a few sparse glandular trichomes to 0.2 mm long as well; capsule densely pubescent with glands (0.05–) 0.1– 0.4 mm long; leaf blades ovate-elliptic to obovate-elliptic to obovate; Pacific versant........................................... L. purpusii