Decalobanthus elmeri (Merr.) A.R.Simões & Staples

Staples, G., 2022, A synoptic revision of the golden glories, genus Decalobanthus (Convolvulaceae), Blumea 67 (1), pp. 37-70 : 52-54

11. Decalobanthus elmeri (Merr.) A.R.Simões & Staples — Fig. 8 ; Map 9

Decalobanthus elmeri ( Merr.) A.R. Simões & Staples (2017) 571. — Merremia elmeri Merr. (1929) 261. — Lectotype (designated here): Elmer 20396 (holo PNH†; lecto UC [ UC 312124 ]*; isolecto A [00054675, 00054676],B [B_10_0241996],BISH [ BISH1001148 ],BO,F [ F0054919 F], G [ G00227278 ], K [ K000830844 ], L [ L 0004225 ],M [ M0184783 ], MO [MO-694472], NY [ NY00336582 ],PNH, SING [ SING0052312 ], U [ U 0001429 ]), ( Malaysia,) British North Borneo (Sabah), Elphinstone province ( Tawau district ), Tawao.

Merremia elmeri Merr.var. glaberrima Ooststr.(1939b) 359. — Decalobanthus elmeri (Merr.) A.R.Simões & Staples var. glaberrimus (Ooststr.)A.R. Simões & Staples (2017) 571. — Type: Hallier 3370 (holo L [ L 0004226 ]; iso BO sheet numbers 935.7 2025a, 935.7 2025b,935.7 2025c, K [ K000830843 ], L [ L 0004227 ], P [ P00600291 ], SAR × 2), ( Indonesia, Kalimantan Barat, Sungai Kenepai,) ‘Borneo. W. Division, Sungai Saniai’ .

Stems not lenticellate; all parts glabrous or reddish hairy. Leaves peltately attached, broadly ovate to orbicular, 6–25 by 5–21 cm, bases rounded to slightly retuse; secondary veins 8–10 on either side of the midvein. Inflorescences 1 or 2 in leaf axils, many-flowered, corymbose; lowermost bracts sometimes foliaceous, not peltate, upper bracts tiny, caducous. Flower buds ovoid, acute or obtuse; sepals subequal, broadly elliptic to elliptic-oblong, 0.9–1.3(–1.5) cm long, convex, obtuse, longitudinally striate abaxially; corollas funnelform-campanulate, 3–3.5 cm long, white, outside minutely granulose-glandular, tube base greyish, limb recurved; stamens protruding, anther connectives villose (or glabrous); pistils protruding, shorter than stamens. Fruiting calyxes slightly accrescent, cupping fruit; sepals blackish abaxially. Capsules subglobose-conical, 1.3– 1.4 cm diam, several-valved, pericarp striate outside. Seeds 4, 5–6.5 mm long, brownish black, short-pubescent, margins with longer hairs.

Previously published illustrations — Van Ooststroom (1939b: 349, f. 3d, 3e).

Distribution — Formerly thought to be endemic to Borneo ( Brunei, Malaysian Sabah and Sarawak, Indonesian Kalimantan Barat, K. Tengah, K. Timur); recently one collection seen from Bacan Island on the eastern side of Sulawesi. Not documented, so far, on the island of Sulawesi, which lies in between.

Habitat & Ecology — Found in diverse kinds of natural areas like mixed dipterocarp forest, rain forest, primary forest clearings, steep hilly country, edges of swamps, riverbanks; as well as in disturbed habitats: along logging roads, in abandoned ladang at roadside in belukar about 2 years old, covering open thickets in wet places in newly cleared land, secondary forest. Numerous soil types are recorded: clay-rich alluvium, red clay, yellow loam, alluvial sandy clay, sand; elevations range from sea level to 550(–1280) m.

One collector noted that the vigorous vines can become “a dangerous weed in young rubber” (H.F. Comber 4085).

Typification — Merrill (1929: 7) stated that the holotypes for his new species are in the Philippine National Herbarium (PNH) with isotypes in UC. However, the holotype for M. elmeri was destroyed during the second World War and the sheet now filed in PNH is an isotype obtained after the war (D. Madulid pers. comm. 2011) . I am therefore designating a lectotype using the duplicate in UC, which has Elmer’s handwritten field notes attached to the sheet.

Notes — Morphologically similar to D. peltatus in the peltate leaf attachment and mainly differing by its smaller and more numerous flowers; the corollas are always white and minutely granulose-glandular outside; the corolla tube bases are greyblack inside and out. Also, many specimens of D. elmeri have dense indumentum on the axial parts as well as the abaxial surfaces of the leaves (glabrous in D. peltatus ).

There is an intriguing comment on the label of Coode & Ferguson 7368 from Brunei: “Flowers creamy-yellow, opening in mid-afternoon, withered by 10 a.m. next morning – in contrast with the bright yellow Merremia which is open all the time.” Could it be that D. elmeri is nocturnally flowering? Further field observations are needed on this point.

Figures

Fig. 8 Decalobanthus elmeri (Merr.) A.R.Simões & Staples. a. Leaves showing peltate attachment of petioles; b. inflorescence with many buds in a more or less flat-topped, corymbiform arrangement; c. flower showing wide-spreading corolla limb and stamen filaments (all Ong Jyh Seng, no voucher).