Trees, shrubs, lianas, vines, or erect or prostrate herbs.
Leaves opposite (except Elytraria), petiolate, simple;
blades entire to serrate; venation pinnate; linear cysto- liths often present; stipules lacking. Flowers bisexual, usually zygomorphic (± regular in Trichanthera), soli- tary or on axillary or terminal, bracteate scapes or spikes;
calyx deeply lobed (reduced in some); corolla tubular, bilabiate, brightly colored; stamens 4 and didynamous or 2, attached to corolla tube; anthers 2-celled, sometimes widely separated by a connective, dehiscing longitudi-
129-ACANTHACEAE 783
KEY TO THE SPECIES OF ACANTHACEAE Plants trees, shrubs, or vines, usually more than 1.5 m tall:
Plants vines, herbaceous or woody:
Bracts subtending flowers linear, ca 1 mm wide; flowers solid white; plants usually less than 4 m tall Justicia graciliflora (Standl.) D. Gibs.
Bracts subtending flowers ± ovate or oblong, more than 1 cm wide; flowers white marked with violet-purple; plants usually vines twining high in forest:
Bracts conspicuously pubescent with ascending trichomes; corolla less than 3.5 cm long ...
Mendoncia gracilis Turr.
Bracts glabrous or with short, sparse puberulence, not ascending; corolla more than 3.5 cm long Mendoncia littoralis Leonard Plants trees or shrubs:
Flowers reddish:
Inflorescences with many, imbricate, red-orange bracts; blades conspicuously pubescent on both sides; corolla tubular and zygomorphic Aphelandra sinclairiana Nees Inflorescences lacking large red-orange bracts; blades glabrous except for veins below;
corolla ± campanulate Trichanthera gigantea (H. & B.) Nees Flowers white or purple:
Flowers white; shrubs vinelike, in the forest Justicia graciliflora (Standl.) D. Gibs.
Flowers purplish; shrubs cultivated in the Laboratory Clearing Thunbergia erecta (Benth.) T. Anderson Plants herbs or suffruticose shrubs usually less than 1 m tall:
Bracts of inflorescence at least in part ovate to obovate, not several times longer than broad:
Flowers and bracts less than 6 mm long; bracts with dense, woolly trichomes; weed in open areas Nelsonia brunellodes (Lam.) O. Kuntze Flowers and bracts usually more than 10 mm long; bracts not densely woolly-pubescent:
Corolla distinctly bilabiate, white with lavender markings medially on inside of lower lip;
plants rare, in the forest along trails Herpetacanthus panamensis Leonard Corolla not distinctly bilabiate (sometimes slightly bilabiate), white to lavender throughout:
Corolla less than 1.5 cm long; plants low, often sprawling, growing in clearings Blechum brownei Ant. Juss.
Corolla more than 2 cm long; plants usually erect, often markedly suffruticose, growing along forest trails Blechum costaricense Oerst.
Bracts of inflorescence all slender, several times longer than broad:
Flowers in loose, open, terminal panicles Justicia pectoralis Jacq.
Flowers usually closely aggregated in leaf axils or in dense terminal heads or spikes:
Spikes borne on slender scapes 5-20 cm long Elytraria imbricata (Vahl) Pers.
Spikes sessile or nearly so:
Inflorescences terminal on stems and branches:
Inflorescences often longer than broad; bracts ca 6 mm long; flowers ca 5 mm long, white with the lower lip violet Teliostachya alopecuroidea (Vahl) Nees Inflorescences as broad as or broader than long; bracts usually more than 15 mm long;
flowers ca 4 cm long, lavender to violet Chaetochlamys panamensis Lindau*
Inflorescences axillary, at most nodes, at least in upper part of stem:
Flowers few at each node, the corolla more than 2 cm long, lavender or lavender tinged with white; plants in the forest along trails Ruellia metallica Leonard Flowers densely clustered at each node, the corolla 6-8 mm long, white; plants on
sandbars and at the edge of the lake Hygrophila guianensis Nees '"Chaetochlamys panamensis is not included in the flora, but since it is a
weedy plant likely to occur on the island it is included in the key.
nally; ovary superior, 2-carpellate, 2-locular; placentation axile; ovules 1 to several, anatropous or amphitropous;
style 1, slender; stigma cupular to 2- or 3-lipped, some- times with 1 lip reduced. Fruits usually loculicidal, obpandurate capsules (drupes in Mendoncia); seeds usu- ally disk-shaped, lacking endosperm, usually forcibly discharged by jaculators (retinacula, hooklike processes on the placenta).
Recognized by their usually densely bracteated inflo-
rescences with a two-lipped corolla and by the cysto- liths in the leaves.
Most Acanthaceae flowers are small and are probably pollinated by small to very small bees. Aphelandra is probably hummingbird pollinated, and Mendoncia and Trichanthera gigantea are possibly bat pollinated. The pollination systems of Justicia graciliflora and Thunbergia erecta, which have larger flowers, are unknown.
The fruits are typically bivalved, often obpandurate
784
DICOTYLEDONEAEcapsules with disk-shaped seeds that are thrown free from the capsules by springlike arms (jaculators or reti- nacula). Van der Pijl (1968) reported that the seeds of some species of Hygrophila have appressed trichomes that become erect and slimy when wet, apparently in- creasing buoyancy and aiding in establishment of the seed. Van der Pijl also reported that the capsules of some species of Ruellia split after a weak spot becomes wet, but this would effect seed dispersal only when soil mois- ture might be adequate for germination of the seed.
Elytraria, Nelsonia, and Mendoncia lack retinacula.
Mendoncia fruits are animal dispersed, probably by birds.
Some 250 genera and about 2,500 species; widely distributed in the tropics.
APHELANDRA R. Br.
Aphelandra sinclairiana Nees in Benth., Bot. Voy.
Sulphur 146, t. 47. 1846
Shrub, 1.5-3.5(6) m tall; stems densely pubescent with erect trichomes. Leaves thin; petioles and midribs below with pubescence like stem; blades oblanceolate, acumi- nate, gradually tapered and decurrent onto petiole nearly to base, 10-38 cm long, 3.5-9.5 cm wide, glabrate above except on major veins, densely pubescent below. Inflo- rescences terminal, densely fine-pubescent, the spikes few to several, densely bracteate, to 13 (20) cm long, the bracts
± obovate, acute or abruptly acuminate, 1-2 cm long, red-orange; sepals 5, acute, subtended by 2 similar bracts;
corolla tubular, 6-7 cm long, magenta, bilabiate, the upper lip 4-lobed, the lateral lobes very short, the lower lip entire, reflexed; stamens 4, stiffly erect, somewhat enfolded in and almost equaling upper lip; anthers open at anthesis, held together, with densely pubescent lateral margins; filaments fused to tube near base; style slender, equaling and held between fused stamens; stigma cupular, bilabiate, open at anthesis; nectary not obvious but with the nectar accumulating at base of corolla tube. Capsules 2-valved, puberulent, ca 2.5 cm long; seeds disk-shaped, ca 4 mm long, suspended on a long, recurved retinac- ulum. Croat 7760.
Occasional, in the forest. Flowers usually continuously throughout the dry season (December to April); the flow- ers appear in succession, usually only a single one at a time from each spike, opening in the morning and usually falling off or wilting before the day is out. The fruits develop quickly, and the lower bracts usually contain mature capsules by the middle of the dry season. Though plants continue to flower in the late dry season (even rarely into the rainy season), the spikes are usually heavy with mature capsules.
No doubt hummingbird pollinated.
Costa Rica and Panama. In Panama, known from trop- ical wet forest in Bocas del Toro (Quebrada Huron), Colon (Rio Buenaventura), Code (above El Valle), and Panama (southwest of Cerro Brewster), but perhaps more abundantly from tropical moist forest on both slopes of the Canal Zone.
BLECHUM P. Browne ex Ant. Juss.
Blechum brownei Ant. Juss., Ann. Mus. Natl. Hist.
Nat. 9:270.1807
B. brownei Ant. Juss. forma puberulum Leonard; B. pyra- midatum (Lam.) Urban
Erect or more commonly sprawling herb, to 70 cm long;
stems slender, glabrate to crisp-villous, the pubescence often restricted to lines. Petioles short or to 1.5 cm long;
blades ovate to ovate-elliptic, acute to acuminate, rounded to attenuate at base, 1.5-5 cm long, 1-3 cm wide, nearly glabrous to densely pubescent usually with a mixture of short, fine trichomes and larger, coarse, often jointed trichomes, the margins usually markedly ciliate; cystoliths very conspicuous, easily confused with trichomes. Flow- ers in close, terminal, bracteate clusters, the bracts more densely pubescent than leaves, ovate to lanceolate, 5-20 mm long, long-ciliolate; calyx deeply divided, to 3.7 mm long, pubescent, the lobes linear-lanceolate; corolla white or sometimes pale lavender, short-pilose especially on tube, 10-13 mm long, the tube 2.5-3 mm diam, the limb ca 8 mm diam, the short lobes rounded, ciliate; stamens 4, held within tube; filaments fused to one side of tube much of their length, one pair shorter; style held to one side of tube between stamens, one lobe reduced, the other lobe directed into center of throat above anthers.
Capsules obovate, 5-6 mm long, densely pubescent, 2-valved, bursting open at maturity to expel several seeds on retinacula; seeds small, dark brown, disk-shaped, ca 1.5 mm diam. Croat 4604, 6966.
Abundant in clearings, especially in the Laboratory Clearing. Flowers and fruits principally throughout the dry season (December to May), though flowering also occurs rarely during the rainy season. Plants have often lost many of their leaves by the end of the dry season when the inflorescences contain mostly fruits.
Mexico (east and south) to Guyana, Ecuador, and Peru;
West Indies, Galapagos Islands; Oceania. In Panama, an ecologically variable weed; known from tropical moist forest in the Canal Zone, Bocas del Toro, San Bias, Chiri- qui, Los Santos, Herrera, Panama, and Darien, from premontane dry forest in Los Santos, from tropical dry forest in Code and Panama, and from premontane wet forest in Panama (Cerro Campana).
See Fig. 505.
Blechum costaricense Oerst., Vidensk. Meddel.
168. 1854
Erect or suberect herb, to 1 m tall, often suffruticose;
stems pubescent with crisp, apically recurved trichomes mostly in lines above petioles on either side; internodes swollen, often darkened. Petioles 5-25 mm long, of- ten narrowly winged; blades ovate to ovate-elliptic, lanceolate-elliptic, or lanceolate, acuminate, attenuate to rounded and decurrent onto petiole at base, 4-12 cm long,
1-4.5 cm wide, the upper surface often with stout simple trichomes, the midrib usually appressed-pubescent (at least near base), the lower surface glabrate to moderately pubescent with short fine trichomes, the margins glabrous
129-
ACANTHACEAE/HERPETACANTHUS785
to ciliate; veins hispidulous to short-villous; cystoliths very conspicuous, easily confused with trichomes. In- florescences loosely bracteate, terminal; flowers each subtended by 2 linear bracts ca 1 cm long and 1 ovate bract 1.5-2.5 cm long; all bracts puberulent, conspic- uously ciliolate; calyx with slender, sharp lobes divided to near base, to ca 5 mm long; corolla ± salverform, 2-3 cm long, hispidulous outside, glabrous inside, lavender- blue above especially on lobes (rarely white), the lobes ca 5 mm long, rounded, the tube 2.5-3 mm diam, whitish, bent outward from below middle; stamens 4; filaments with the basal one-half to two-thirds fused to tube, affixed to one side of tube somewhat below rim, the inner pair held below outer pair; anthers dehiscing introrsely; pollen somewhat tacky, clinging together in small clusters; style slender, held along staminal side of tube; stigmas densely puberulent, 2-lipped, with one lip very reduced, the other extending across mouth of tube, recurved. Capsules ovoid, 5-8 mm long, somewhat flattened, apically beaked, pu- berulent; seeds disk-shaped, 2-3 mm diam, brown, the outer margin quickly becoming swollen and sticky upon wetting. Croat 4365 (typical), 7445 (narrow-leaved form).
Frequent along trails in the forest. Flowers mostly throughout the dry season (December to May), rarely flowering and fruiting during the rainy season. The fruits develop quickly.
The small pollinator probably enters the tube to effect pollination, the style acting as a brush to remove pollen picked up from a previous visit. Pollen is probably de- posited on the insect's body when it passes the anthers.
Similar to B. brownei in most respects but tending to be more robust and erect, to have much larger flowers and leaves, and not to grow in open areas.
Standley reported this species as B. panamense Lindau, which, if considered distinct from B. costaricense, does not occur on BCI. Leonard has annotated some BCI col- lections as B. dariense Lindau. Both B. panamense and B.
dariense reportedly have corollas less than 1.7 cm long, whereas most of the plants observed in the forest on BCI have corollas 2.5-3 cm long. Perhaps some hybridization takes place between B. brownei and B. costaricense, since plants in the forest that grow closest to populations of B. brownei frequently have the long trichomes on the upper leaf surface associated with that species. Plants farther away in the forest tend to be nearly glabrous on the upper leaf surface.
Costa Rica and Panama. In Panama, known princi- pally from tropical moist forest on the Atlantic slope in the vicinity of the Canal Zone; known also from tropical moist forest in Chiriqui and Darien and from premontane wet forest in Chiriqui (near Conception) and Panama.
ELYTRARIA Michx.
Elytraria imbricata (Vahl) Pers., Synops. PI. 1:23. 1805 Acaulescent to caulescent suffruticose herb, to ca 60 cm tall; stems ± glabrous. Leaves alternate to subopposite;
blades mostly ovate to oblanceolate, acute to acuminate, gradually narrowed to slender winged petiole, 3-12 cm
long, 1.5-4 cm wide, glabrate to sparsely villous espe- cially on veins, the margins ± undulate and ciliate; cysto- liths apparently lacking. Inflorescences of numerous, upper-axillary or terminal, simple or branched scapes mostly 5-25 cm long (sometimes leafy at apex), closely bracteate, the bracts firm, usually subulate, keeled, with villous margins; spikes 1 to several per scape, to 6 cm long and ca 5 mm wide, the bracts firm, awned-tipped and bearing a pair of thin wings near apex, glabrous out- side, densely pubescent inside; bracteoles subulate, ca 3 mm long, the costa ciliate; calyx segments 2, unequal, narrow, the posterior one bidentate; corolla bluish, 5-8 mm long, the tube slender, the limb bilabiate, the lower lip trilobate; stamens 2, barely exserted; anther thecae connate, ca 0.5 mm long; pistillate parts not seen. Cap- sules narrowly conical, ca 3 mm long and 1 mm diam, glabrous; seeds lacking retinacula. Croat 6963.
Rare, on a shady steep slope in the Laboratory Clear- ing. Flowers in the early dry season. The fruits develop quickly and seeds are dispersed in the dry season as well.
Arizona and Texas through northern and western South America to Ecuador and Brazil (Mato Grosso and Rio de Janeiro). In Panama, known from tropical moist forest in the Canal Zone, Colon, Los Santos (Tonosi), and Panama, from tropical dry forest in Herrera (Pese), Code (Penonome), and Panama (Taboga Island), and from premontane wet forest in Chiriqui.
HERPETACANTHUS Nees
Herpetacanthus panamensis Leonard, J. Wash. Acad.
Sci. 32:185. 1942
Suffruticose herb, 1 m or more tall, often rooting at basal nodes; stems terete, nodose, brittle, easily breaking at nodes; younger parts with uncinate trichomes. Petioles 3-5 mm long; blades elliptic, acuminate, attenuate and
± decurrent at base, 5-14 cm long, 2.5-7.5 cm wide, essentially entire, glabrous and shiny above with minute linear cystoliths, duller on lower surface; veins strigose, the major lateral veins ± impressed, the reticulate veins conspicuous. Inflorescence bracteate, terminal and axil- lary, the bracts ovate, acute, pubescent, ciliate; calyx regular, sparsely pubescent, to 5 mm long, deeply lobed, the lobes linear; corolla funnel-shaped, ca 2 cm long, bilabiate, white with lavender markings medially inside on lower lip, glabrous except on lower part of tube inside and on outside of lobes, the tube narrow, the upper lip narrowed to an emarginate tip, the lower lip trilobate;
stamens 4, the upper pair with the thecae broadly sep- arated and at different levels on connective; filaments united, the tube ca 1 cm long; anthers 1.2 mm long, longi- tudinally dehiscent; pistil cylindrical, pubescent, minute;
style more than 1 cm long, pubescent; stigmas 2. Fruits capsular, ca 1 cm long, brown; seeds disk-shaped, ca 2 mm diam. Croat 11900.
Rare, in open areas of the forest. Seasonal behavior not determined. Collected on BCI in flower in August.
Costa Rica and Panama. In Panama, known from tropical moist forest in the Canal Zone (Atlantic slope)
Fig. 505. Blechum brownei
Fig. 506. Justicia graciliflora
Fig. 508. Mendoncia littoralis
Fig. 507. Mendoncia gracih
and Bocas del Toro and from tropical wet forest in Colon (Santa Rita Ridge).
HYGROPHILA R. Br.
Hygrophila guianensis Nees, London J. Bot.
4:634. 1845
Herb, to 1.2 m tall, sparsely hirtellous to glabrate; stems obtusely quadrangular, branched. Blades lanceolate to lanceolate-linear, acuminate at apex, gradually attenu- ate at base to an obscure, winged petiole, 5-16 cm long, 0.5-4 cm wide, entire; cystoliths dense but ± obscure.
Flowers sessile, in dense axillary clusters subtended by linear-lanceolate bracts; calyx 5-9 mm long, deeply lobed, the lobes ± linear; corolla white, bilabiate, 6-8 mm long, puberulent, the tube ca 1 mm diam, the upper lip bidentate, ca 2.5 mm long, the lower lip trilobate;
stamens 4, arranged in 2 unequal pairs and fused to tube at base; pistillate parts not seen. Capsules narrowly ob- long, acute at apex, 9-12 mm long, ca 1.5 mm wide, gla- brous; seeds 16-18, disk-shaped, less than 1 mm wide, brown, the margin discolorous and becoming sticky on wetting. Croat 6402.
Frequent on sandbars in lagoons around the edge of the island, especially on the western side. Flowers from November to March, especially from December to Feb- ruary. Since the fruits develop quickly, the same inflores- cence may bear both flowers and fruits.
Mexico to central Argentina; West Indies; in marshy areas and along water courses from sea level to 1,500 m.
In Panama, ecologically variable; known from tropical moist forest in the Canal Zone and Panama, from pre- montane dry forest in Code (Anton), and from tropical wet forest in Bocas del Toro (Santa Catalina).
JUSTICIA L.
Justicia graciliflora (Standl.) D. Gibs., Fieldiana, Bot.
34:69. 1972
Beloperone graciliflora Standl.
Vine or clambering shrub, 1-4 m long; stems moderately pubescent when young, glabrate in age. Petioles 5-8 mm long, often pubescent; blades lanceolate to nar- rowly elliptic, short-acuminate, acute to obtuse and decurrent at base, glabrous with many prominent cysto- liths. Panicles terminal, 4-8 cm long, sessile or short- pedunculate, bearing few flowers, the bracts linear, green, 5-7 mm long, ca 1 mm wide; pedicels ca 1 cm long;
sepals lanceolate-linear, 2-2.5 cm long, 3-5 mm wide, pale orange, glabrate with linear cystoliths; corolla white, the tube narrow, 3-5 cm long, the limb bilabiate, to 2 cm long, the lower lip deeply, equally trilobate; stamens 2, nearly equaling upper lip; thecae of anthers large, unequal; pistillate parts not seen. Capsules spatulate to oblong, 1.5-2 cm long, rounded and apiculate to acute at apex, obtuse at base, glabrate; seeds subglobose, ca 3.3 mm diam, brown, glabrous. Croat 7372, Shattuck 602 (type).
129.
ACANTHACEAE/MENDONCIA787
Uncommon, in the old forest; collected on Armour, Drayton, and Wheeler trails. Flowers from late Novem- ber to late January. Mature fruits have been seen in March. On BCI the plant has not been found in the canopy, but it was found growing at about 25 m in a tree in Veraguas Province.
Known only from Panama, from tropical moist forest on BCI and in Darien and from premontane wet forest in Veraguas (west of Santa Fe) and Panama (Cerro Jefe).
See Fig. 506.
Justicia pectoralis Jacq., Enum. PL Carib. 11. 1760 Erect herb, to 50(100) cm tall; stems with lines of retrorse pubescence between leaves, often decumbent and rooting at basal nodes. Leaves decussate; petioles 2-12 mm long;
blades lanceolate, long-acuminate, acute to obtuse at base, 2-11 cm long, 0.4-2.5 cm wide, ± glabrous except for upper midrib; cystoliths moderately conspicuous above under magnification. Panicles terminal, dichoto- mous, to 15 cm long, the branches broadly divergent, densely puberulent, with longer glandular trichomes;
bracts ca 2 mm long, 1 mm wide; flowers sessile, sparse;
calyx ca 2.5 mm long, the pubescence as on inflorescence branches, the lobes long, sharp, the uppermost shorter;
corolla bilabiate, lavender except for white base, the upper lip sparsely pubescent outside, narrow, folded, enclosing style in medial groove, the lower lip trilobate, its middle lobe corrugated with prominently raised, white, lateral veins extending into tube on either side of medial groove; stamens 2, affixed laterally, arching to center; anthers horseshoe-shaped, loosely clasping style;
style slender, 7-8 mm long, curved downward at apex.
Capsules club-shaped, acute at apex, 6-8 mm long, 1.5 mm broad, puberulent; seeds ca 1.5 mm broad, covered with papillae, the papillae minute, immediately becoming sticky upon wetting. Croat 10253.
Occasional, in clearings, especially along the path in the Rear Lighthouse Clearing. Flowers from December to May. The fruits develop quickly and are dispersed in the dry season.
Pollination is effected by a small insect, which crawls into the tube (no doubt with the corrugated, somewhat downturned lower lip acting as a landing platform). In crawling beneath the arched stamens, it spreads pollen on its back. At the same time the style is released from its groove and strikes the pollinator's back.
Wide-ranging and weedy throughout the New World tropics, including the West Indies. In Panama, known from tropical moist forest in the Canal Zone (both slopes), Colon, Chiriqui (David), Panama, and Darien and from premontane wet forest in Panama (Chiman).
MENDONCIA Veil, ex Vand.
Mendoncia gracilis Turr., Kew Bull. 1919:418. 1919.
Vine; stems, petioles, and blades pubescent, the trichomes sparse to dense, moderately long, ± appressed; stems angulate. Petioles canaliculate, ridged above, 1.5-2.5 cm