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 Epiphytes with large, conspicuous ant-inhabited tubers

 

- Tubers unarmed; leaves to 9 cm long, elliptic to elliptic-oblong or obovate

 .........................................................................................Hydnophytum*

- Tubers with short thorns; leaves at least 10 cm long, elliptic

 .........................................................................................Myrmecodia*

Trans. Linn. Soc. London 14: 122. 1823; Beccari, Malesia 2: 95. 1884; Huxley & Jebb, Blumea 37: 274. 1993; Puff et al., Rubiaceae of Thailand: 170 & pl. 3.3.3. 2005.

 

Epiphytic plants with swollen, tuberous bases (hypocotyls tubers); the tubers, with numerous ant-inhabited cavities, often ridged and with short thorns (modified adventitious roots). A thick, solitary, unbranched stem arising from the tubers [outside Thailand sometimes also a few stems]. Leaves opposite, petiolate, blades coriaceous; stipules often persistent, splitting between the petioles. Inflorescences sunken into the stem axis; inconspicuous or with hairs forming a dense mass. Flowers 4-merous, sessile, often heterostylous. Calyx small and indistinct. Corolla white, infundibular, the lobes uncinate, not usually spreading at anthesis; the tube with a ring of hairs at varying levels. Stamens subsessile, anthers enclosed in tube. Ovary (2-)4-6(-10)-locular, each locule with an erect solitary ovule; style short or long, the stigma (2-)4-6(-10)-lobed. Fruits drupaceous, with (2-)4-6(-10) pyrenes.

 

A genus of c. 26 species confined to Malesia and surrounding areas; 1 very widely distributed species reaching the southernmost part of Thailand.— Classification: subfamily Rubioideae, tribe Psychotrieae.

 

Myrmecodia tuberosa Jack, Trans. Linn. Soc. London 14: 122. 1823; Beccari, Malesia 2: 99, t. 13, 14. 1884; Huxley & Jebb, Blumea 37: 276. 1993.

 

Ant-inhabited tuberous epiphyte. Tuber irregularly globose to oblong, to 40 by 15 cm, usually ridged, with entrance holes arranged in irregular arcs and with simple thorns mostly on the ridges; apically with a thick, solitary, unbranched erect or upward-curving stem to c. 30 cm long. Leaves thinly coriaceous, elliptic, 10-18 by 4-7 cm, narrowed to the base, apex acuminate, glabrous; petioles 2.5-5 cm long; stipules  broadly triangular, falling before the leaves, to c. 1 cm long. Flowers small, bisexual, sessile, in clusters of few sunken into the stem axis. Calyx to c. 1 mm long. Corolla white, tube to c. 8 mm long, with a ring of hairs near its base, lobes c. 3-4 mm long, not fully opening at anthesis. Stamens inserted in upper part of tube, anthers < 1 mm long. Ovary 4-6-celled, < 1 mm high; style and 4-6-lobed stigma as long as or shorter than corolla tube. Drupe yellow to orange, ovoid to subglobose, crowned by persistent calyx, to c. 7 mm long, with 4-6 pyrenes. 

 

T h a i l a n d.— PENINSULAR: Narathiwat (Hala Bala).

 

D i s t r i b u t i o n.— Throughout Malesia (type: Sumatra) to Australia and the Solomon Islands; also in Vietnam (Annam).

 

E c o l o g y.— . Altitude: < 500 m.

 

V e r n a c u l a r.— ??.

 

N o t e.— Throughout its entire distribution range, the species shows considerable, continuous variation. Thai material agrees with the informal Myrmecodia tuberosa ‘armata’ variant of Huxley & Jebb, Blumea 37: 277. 1993, which occurs from Peninsular Malaysia to Java and Borneo.

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Jack, Trans. Linn. Soc. London 14: 124. 1823; Puff et al., Rubiaceae of Thailand: 166 & pl. 3.3.1. 2005.— Lasiostoma Benth., Hooker's J. Bot. Kew Gard. Misc. 2: 224. 1843.

 

Epiphytic plants with swollen, tuberous bases (hypocotyls tubers); the tubers with numerous ant-inhabited cavities. Several slightly woody, foliate stems arising from the tubers. Leaves opposite, coriaceous, with small, interpetiolar, deciduous or persistent stipules. Inflorescences axillary, solitary at nodes, usually on alternating sides along the length of a branchlet, few-flowered, mostly fasciculate and contracted. Flowers 4-merous, sessile, hermaphrodite (and then usually heterostylous) or unisexual [not in Thailand]. Calyx short-cupular, truncate to shallowly dentate, persistent. Corolla hypocrateriform to narrowly infundibular, glabrous within or variously pubescent in the throat, the lobes valvate in bud, spreading or reflexed, uncinate. Stamens (and staminodia) inserted around corolla throat, with subsessile anthers. Ovary 2-locular, each locule with an erect solitary ovule; style short or long, the stigma 2-lobed. Fruits brightly colored, drupaceous, mostly (ob)ovoid to turbinate, with 2 pyrenes.

 

A genus of about 50 species occurring from the Andamans, Myanmar and Indochina throughout Malesia to the SW. Pacific; 1 very widely distributed species also in Thailand.— Classification: subfamily Rubioideae, tribe Psychotrieae.

 

Hydnophytum formicarum Jack, Trans. Linn. Soc. London 14: 124. 1823; Hook.f., Fl. Br. Ind. 3: 195. 1881 (pro parte); Ridl., Fl. Mal. Pen. 2: 172. 1923; Pitard in Fl. Gén. I.-C. 3(3): 406. 1924; Craib in Fl. Siam. En. 2(2): 223. 1934.— Lasiostoma formicarum (Jack) Spreng., Syst. Veg. 1: 423. 1824.— Hydnophytum formicarum Jack forma cochinchinense Beccari, Malesia 2: 163. 1885; Pitard in Fl. Gén. I.-C. 3(3): 407. 1924.— Hydnophytum formicarum Jack forma siamensis Beccari, Malesia 2: 167, fig. 12-17. 1885.

 

Ant-inhabited tuberous epiphyte. Tuber cylindrical to spherical or rather irregularly shaped, in old individuals up to ca. 25-30 cm long, with entrance holes scattered over its surface, without thorns; apically with several unbranched to branched erect stems to c. 30 cm long. Leaves coriaceous, elliptic to elliptic oblong or obovate, 5-9 by 2.5-6 cm, narrowed to the base, obtuse at apex, glabrous; petioles 2-5 mm long. Flowers small, bisexual, sessile, in axillary clusters of few. Calyx with short tube, truncate above, < 1 mm high. Corolla white, tube hairy around the throat, c. 3 mm long; lobes oblong, shorter than to as long as the tube. Stamens inserted below throat, anthers subsessile, included. Ovary < 1 mm high; style with 2-lobed stigma included. Drupe orange to orange-red, ovoid, crowned by persistent calyx, c. 5 mm long; the 2 pyrenes plano-convex, blackish.  

 

T h a i l a n d.— EASTERN: Si Sa Ket; SOUTH-EASTERN: Chachoengsao, Chanthaburi, Trat; PENINSULAR: Phangnga, Krabi, Trang, Satun, Songkhla, Narathiwat.

 

D i s t r i b u t i o n.— Myanmar, Vietnam; throughout Malesia to New Guinea (type Sumatra).

 

E c o l o g y.— In lowland evergreen rain forest, peat swamp forest, beach forest, occasionally in seasonal rainforest. The species does not seem to have any preferred host trees; plants either cling to tree trunks or grow on main crown branches of trees of various heights. Not infrequently forming large populations and often associated with other obligatory or facultative ant-plants such as the ant-fern Lecanopteris (Polypodiaceae) or Dischidia spp. (Apocynaceae). Altitude: 0–500(?) m.

 

V e r n a c u l a r.— ??.