ACANTHACEAE

Daniel, Thomas F., García-Morales, Leccinum J. & Mora-Olivo, Arturo, 2021, Taxonomic and Photographic Guide to the Acanthaceae of Tamaulipas, Mexico, Proceedings of the California Academy of Sciences 67 (6), pp. 185-228 : 188-191

KEY TO THE GENERA AND SPECIES OF TAMAULIPAN ACANTHACEAE

1a. Mangrove trees or shrubs with pneumatophores; fruit a leathery and tardily dehiscing/non-explosive capsule with 1 seed...................................................... Avicennia germinans

1b. Herbs, shrubs, or vines, pneumatophores absent; fruit a woody and explosively dehiscent capsule with 2 or more seeds........................................................................ 2

2a. Seeds not borne on hooklike retinacula (retinacula absent or papilliform); plants without cystoliths; anthers 2-thecous............................................................................ 3

2b. Seeds borne on conspicuous hooklike retinacula; plants with cystoliths (or if plants without cystoliths, then anthers 1-thecous); anthers 2-thecous or 1-thecous........................................... 4

3a. Caulescent twining vines; leaves opposite on elongate stems; inflorescence of 1-flowered pedunculate dichasia in leaf axils, peduncles naked; stigma not touch-sensitive; calyx inconspicuous, shallowly 11–17- lobed; capsule with a prominent sterile distal beak longer than the fertile globose base; pollen spiraperturate............................................................... Thunbergia

a. Petioles alate; leaf blades sagittate; corolla orange, throat dark purple, internally glandular; thecae pubescent, at least 1 theca per anther with a prominent basal appendage; capsule 14–23 mm long.................................................................... T. alata

a’. Petioles naked; leaf blades ovate to narrowly ovate-deltate; corolla entirely white (or with throat faintly yellow), throat internally eglandular; thecae glabrous, lacking basal appendages; capsule 22–27 mm long......................................................... T. fragrans

3b. Acaulescent or subcaulescent perennial herbs; leaves in a basal cluster; inflorescence borne on peduncles covered with coriaceous and clasping scales; stigma touch-sensitive; calyx deeply 4-lobed, anterior lobe shallowly 2-parted; capsule without a prominent sterile distal beak (beak, if present, considerably shorter than fertile portion of capsule); pollen 3-colpate...................................... Elytraria

a. Leaves 4. 5–25 mm wide; bracts lanceolate, 6–11 mm long; calyx 6–8 mm long; corolla pinkish to

nearly white.......................................................... E. bromoides

a’. Leaves 27–112 mm wide; bracts broadly ovate, 3.8– 5 mm long; calyx 4.5– 5.2 mm long; corolla yellow............................................................... E. macrophylla

4a. Calyx 3-lobed, 32–47 mm long; corolla whitish to greenish cream, lacking colored markings, 55–60 mm long, throat prominently saccate (forming a conspicuous pouch); pollen pantoforate................................................................................ Louteridium tamaulipense

4b. Calyx 4- or 5-lobed, 1–30 mm long; corolla not with the above combination of characters; pollen not pantoforate.......................................................................... 5

5a. Stamens 4, sometimes also with an additional staminode..................................... 6

5b. Stamens 2, sometimes with additional staminodes.......................................... 12

6a. Corolla lemon yellow turning dark blue-purple or blackish on drying; calyx deeply 4-lobed, lobes heteromorphic with outer (anterior and posterior) lobes larger than inner (lateral) lobes; anterior lobe apically 2- cleft.............................................................. Barleria oenotheroides

6b. Corolla variously colored, but when yellow, not turning dark blue-purple or blackish on drying; calyx 5- lobed, lobes homomorphic (or if heteromorphic, then not with lobes as described above), anterior lobe apically entire.......................................................................... 7

7a. Cystoliths absent; anthers 1-thecous; corolla lobes ascending-cochlear in bud; pollen 3-colpate....... 8

7b. Cystoliths present; anthers 2-thecous; corolla lobes contorted (left-contort) in bud; pollen otherwise.. 10

8a. Bracts with 2 submarginal clusters of padlike nectaries (up to 16 per cluster) on abaxial surface; corolla reddish, 30–45 mm long, lateral lobes of lower lip much reduced and appearing attached to upper lip, 0.2– 2.5 mm long, lower-central lobe reflexed or usually recoiled; anther thecae 3–4 mm long.................................................................................. A phelandra scabra

8b. Bracts without submarginal clusters of padlike nectaries on abaxial surface; corolla pink, white to cream (often with greenish tinge), or yellow, 9-20 mm long, lateral lobes of lower lip neither reduced nor appearing attached to upper lip, 3. 5-10 mm long, lower-central lobe not reflexed or recoiled; anther thecae 1.2- 2.3 mm long...................................................................... 9

9a. Caulescent shrubs; leaves opposite or whorled; corolla strongly zygomorphic, white to cream (often with greenish tinge) or yellow, limb not rotate; anthers at least partially exserted from mouth of corolla............................................................................... Holographis

a. Leaves opposite; abaxial surface of bracts and bracteoles glabrous; corolla white to cream (often with greenish tinge), 9-12 mm long, externally glabrous; seeds papillose with both minute and larger rounded papillae................................. H. tamaulipica

a’. Leaves usually whorled (rarely opposite on some shoots); abaxial surface of bracts and bracte-

oles pubescent; corolla yellow, 12-20 mm long, externally pubescent; seeds ± smooth...................................................................... H. ehrenbergiana

9b. Acaulescent (to subcaulescent) perennial herbs; leaves in a basal cluster; corolla subactinomorphic, pinkish, limb ± rotate; anthers included in corolla tube............................. Stenandrium dulce

10a. Thecae basally awned or mucronate; pollen 3-colporate, mesocolpia multi-striate with pseudoclopi............................................................................. Dyschoriste

a. Glandular trichomes present on some or all of the following: young stems and leaves, bracteoles,

calyx, and external surface of corolla.................................... D. hirsutissima

a’. Glandular trichomes absent....................................................... b

b. Plants erect, up to 1 m or more tall; leaves ovate to elliptic, not conduplicate (17–) 25–110 mm long, 8–50 mm wide................................................... D. quadrangularis

b’. Plants mostly prostrate, decumbent, scrambling, or if erect, then up to ca. 3 dm tall; leaves linear to oblanceolate to obovate to obovate-elliptic, often conduplicate, 8–33 mm long, 1–11 (–14) mm wide.......................................................................... c

c. Leaves oblanceolate to obovate to obovate-elliptic, margin crenulate-sinuate (at least distally........................................................................ D. crenulata

c’. Leaves linear to linear-oblanceolate, margin entire.................................... d

d. Internodes glabrous or very sparsely pubescent with retrorse trichomes 0.1– 0.2 mm long.......................................................................... D. greenmanii

d’. Internodes ± conspicuously pubescent with flexuose to retrorse trichomes to 0.3 mm long.......................................................................... D. schiedeana

10b. Thecae lacking basal awns or mucros; pollen otherwise.................................... 11

11a. Plants submersed or emergent aquatics, corolla 8–16. 5 mm long (septa and retinacula remaining attached to inner capsule wall at maturity), limb zygomorphic (conspicuously 2-labiate); pollen 4-colporate, mesocolpia each with 2–3 pseudocolpi...................................... Hygrophila corymbosa

11b. Plants terrestrial; corolla 20–60 mm long (or 10–20 mm long in R. blechum , which has septa and attached retinacula separating from inner capsule wall at maturity), limb subactinomorphic; pollen 3-porate.................................................................................... Ruellia

a. Inflorescences of terminal, 4-sided, densely bracteate spikes; calyx 2.5– 5 mm long; corolla 10–20 mm long, limb 4–11 mm in diameter; capsule 5. 5–7 mm long, septa with attached retinacula separating from inner wall of mature capsule.................................... R. blechum

a’. Inflorescence of 1–many-flowered, sessile to long pedunculate, dichasia in leaf axils; calyx (5.5–) 7–25 mm long; corolla 21–70 mm long, limb 10–49 mm in diameter; capsule 8–29 mm long, septa with attached retinacula remaining attached to inner wall of mature capsule................ b

b. Leaves, bracteoles, calyx, corolla, and capsule (at least near apex) beset with conspicuous punctate glands 0.05– 0.1 mm in diameter; inflorescence of sessile to subsessile (peduncles to 1 mm long) dichasia in leaf axils, dichasia 1 (–2)-flowered; capsule 8–11 mm long; seeds 4 per capsule........................................................................ R. hookeriana

b’. Leaves, bracteoles, calyx, corolla, and capsule without conspicuous punctate glands (sparse and/or inconspicuous punctate glands 0.01- 0.1 mm in diameter sometimes evident on abaxial surface of leaves of R. simplex ); inflorescence of pedunculate (peduncles 3–90 mm long) expanded dichasia in leaf axils, dichasia mostly 3–many-flowered (distal dichasia of R. ciliatiflora subsessile to pedunculate in axils of reduced leaves or bracts, congested or expanded, and often forming a terminal leafy thyrse); capsule 10–29 mm long; seeds 8–22 per capsule........................... c

c. Limb of corolla 10–25 mm in diameter; seeds with trichomes restricted to margin, forming a conspicuous marginal band................................................ R. paniculata

c’. Limb of corolla 18–49 mm in diameter; seeds with trichomes covering entire surface and margin.............................................................................. d

d. Internodes of young stems and peduncles of dichasia pubescent with glandular and eglandular trichomes; capsule 10–22 mm long, pubescent with glandular and eglandular trichomes; seeds 8–12 per capsule.......................................................... R. ciliatiflora

d’. Internodes of young stems and peduncles of dichasia usually glabrous (stems sometimes pubescent with sparse eglandular trichomes and peduncles sometimes with a few scattered eglandular or glandular trichomes); capsule 20–29 mm long, glabrous or with inconspicuous glandular trichomes at apex only; seeds 16–22 per capsule......................................... R. simplex

12a. Androecium of 2 stamens and 2 staminodes.............................................. 13

12b. Androecium of 2 stamens and 0 staminodes............................................. 14

13a. Plants submersed or emergent aquatics; corolla 4.5– 5.5 mm long, ± funnelform, tube short, limb zygomorphic (conspicuously 2-labiate); capsule 5–6 mm long, distally pubescent; pollen 3–4-colporate, mesocolpia each with 3–4 pseudocolpi...................................... Hygrophila polysperma

13b. Plants terrestrial; corollas 20–45 mm long, subsalverform, tube elongate, limb subactinomorphic; capsule 10–16 mm long, glabrous; pollen 3-colporate, mesocolpia each with 2 pseudocolpi................................................................................... Pseuderanthemum