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FOC | Family List | FOC Vol. 16 | Convolvulaceae

12. Merremia Dennstedt ex Endlicher, Gen. Pl. 1: 1403. 1841.
[nom. cons.]

鱼黄草属 yu huang cao shu

Skinneria Choisy; Spiranthera Bojer.

Herbs or shrubs, often twining, sometimes prostrate. Leaves usually petiolate, rarely sessile, margin entire, dentate, or palmately or pedately lobed or compound. Flowers axillary, solitary or in few- to many-flowered, variously branched cymose inflorescences; bracts usually small. Sepals variable in shape, often convex, subequal or outer 2 smaller, persistent, often enlarged in fruit. Corolla often yellow or white, sometimes with a darker center, funnelform or campanulate, usually glabrous, or midpetaline bands ± sericeous, sometimes only at apex; limb entire or ± 5-angled. Stamens included, often unequal; anthers often spirally twisted; filaments dilated basally, filiform distally; pollen 3-12-colpate or polyrugate, not spiny. Disc ringlike. Pistil included; ovary (imperfectly 2-)4-loculed, 4-ovuled. Style 1, filiform; stigmas 2-globular. Capsule 1-4-loculed, usually 4-valved or ± irregularly dehiscing. Seeds 4 or fewer, glabrous or pubescent to villous especially at margin.

Approximately 80 species: tropical regions of Africa, Asia, Australia, North and South America; 19 species in China.

The generic name Merremia was published as a nomen nudum by Dennstedt (Schlüssel Hortus Malab. 12, 23, 34. 1818). Several modern floras attribute the valid publication of the name to H. Hallier (Bot. Jahrb. Syst. 16: 581. 1893), but Endlicher (1841) actually validated the name.

Merremia is often confused with Ipomoea, which has pantoporate, spiny pollen, straight anthers and very few species with yellow corollas. It is also confused with Operculina, which consistently has a fruit with a circumscissile lid that detaches first, leaving a fragile endocarp that shatters irregularly. The distribution of hairs on the corolla is taxonomically important in Merremia; this is most easily discerned on mature flower buds.

1 Leaves ± palmately (3-)5-7-lobed or palmately compound, with 5 leaflets.   (2)
+ Leaves entire, irregularly coarsely crenate or serrulate, sometimes 3-lobed.   (5)
2 (1) Leaves palmately compound, leaflets 5, entire   6 Merremia quinata
+ Leaves ± palmately lobed, lobes entire, undulate-lobate, to dentate.   (3)
3 (2) Leaves palmately divided nearly to base, lobes 5 or 7; corolla white, throat purple-red   7 Merremia dissecta
+ Leaves palmately angled or lobed; corolla yellow.   (4)
4 (3) Leaves palmately 5-7-angled or -lobed nearly to middle; outer sepals 14-18 mm, hirsute abaxially; anthers spirally twisted   8 Merremia vitifolia
+ Leaves deeply 3-lobed to below the middle; outer sepals 6-7 mm, glabrous; anthers straight   14 Merremia caloxantha
5 (1) Corolla glabrous outside.   (6)
+ Corolla with midpetaline bands densely sericeous outside at least apically, sometimes throughout.   (13)
6 (5) Peduncle very short or absent; flowers 1-3 per axil; leaves reniform to broadly ovate, 0.5-3.5 mm   5 Merremia emarginata
+ Peduncle distinct; flowers and leaves not as above.   (7)
7 (6) Sepals acuminate or subulate, subequal.   (8)
+ Sepals rounded, obtuse (and apiculate in M. hainanensis), or emarginate, outer 2 clearly shorter than inner ones (± unequal in M.gemella).   (9)
8 (7) Corolla pink, pale purplish, or white, 1.2-1.9 cm; sepals 5-7 mm, subulate-mucronate; leaves ovate-cordate, 3-13 1.7-7.5 cm, apex attenuate or caudate   9 Merremia sibirica
+ Corolla pale yellow, ca. 3 cm; sepals 10-15 mm, acuminate; leaves oblong-elliptic to ovate-lanceolate, 1.8-5 0.8-2.5 cm, apex rounded to acute   10 Merremia collina
9 (7) Inner sepals 8-10 mm; corolla 1.8-2.2 cm.   (10)
+ Inner sepals 5-7 mm; corolla 0.6-1.5(-2) cm.   (11)
10 (9) Pedicel terete; outer 2 sepals abaxially smooth; petiole 1.5-3 cm; Hainan   3 Merremia hainanensis
+ Pedicel verruculose apically; outer 2 sepals verruculose abaxially; petiole 3-8 mm; Guangxi   17 Merremia verruculosa
11 (9) Sepal margins purplish; leaves linear, oblong-lanceolate, ovate-oblong, or ovate, entire, base truncate, rounded, ± auriculate, or hastate   4 Merremia hirta
+ Sepal margins not colored; leaves ovate or ovate-cordate, entire, coarsely crenate, or 3-lobed, base cordate or broadly cordate.   (12)
12 (11) Outer sepals glabrous, all sepals broadly obovate to spatulate or oblong, apex emarginate and distinctly mucronate, mucro directed outward; corolla 0.6-1 cm; stems, petioles, and pedicels tuberculate   1 Merremia hederacea
+ Outer sepals usually ± pilose abaxially, all sepals broadly obovate to ± circular, apex emarginate, not or only slightly mucronulate; corolla 1.5-2 cm; stems, petioles, and pedicels without tubercles   2 Merremia gemella
13 (5) Pedicel with a thick lobed ring immediately below calyx; stems and leaves densely pubescent or mealy, especially when young; extreme S Taiwan   19 Merremia similis
+ Pedicel without a thick lobed ring below calyx; stems and leaves glabrous, or tomentose and later glabrescent; mainland or Hainan (M.umbellata rare in Taiwan).   (14)
14 (13) Corolla lilac, pink, or white; seeds glabrous.   (15)
+ Corolla yellow or white; seeds pubescent, at least on margins (unknown in M.caloxantha).   (16)
15 (14) Leaves rhombic, rhombic-ovate, or nearly circular, base cuneate; corolla narrowly campanulate, 3.5-4 cm   11 Merremia yunnanensis
+ Leaves cordate, base cordate; corolla funnelform, 2-2.5 cm   16 Merremia longipedunculata
16 (14) Outer 2 sepals shorter than inner ones.   (17)
+ All sepals ± equal.   (19)
17 (16) Inflorescences lax cymes, usually 2- to several flowered, rarely flowers solitary; outer sepals elliptic, glabrous; plants with tubers   13 Merremia hungaiensis
+ Inflorescences dense umbelliform or corymbose cymes, flowers few to many; outer sepals broadly ovate or broadly elliptic to nearly circular; tubers absent.   (18)
18 (17) Leaves usually nearly circular, rarely broadly ovate; inflorescence a many-flowered corymbiform cyme; corolla 1.4-2(-3.2) cm, yellow, midpetaline bands densely sericeous   18 Merremia boisiana
+ Leaves usually ovate or ovate-oblong to oblong-lanceolate; inflorescence a few- to many-flowered umbelliform cyme; corolla 2.5-5.5 cm, white (or ?yellow), midpetaline bands pubescent only at apex   12 subsp. orientalis
19 (16) Woody climber, pubescent to tomentose (older parts glabrous); corolla 1.4-2(-3.2) cm, midpetaline bands sericeous throughout their length   18 Merremia boisiana
+ Herbaceous twiner, subglabrous or glabrescent (petioles pilose apically); corolla 3-4 cm, midpetaline bands hairy at apex only.   (20)
20 (19) Leaf blade deeply 3-lobed, 3-3.5 cm; petiole 1.3-2.2 cm; sepals 6-7 mm, all obovate   14 Merremia caloxantha
+ Leaf blade entire, cordate, 5-7 cm; petiole 3-6 cm; sepals ca. 10 mm, outer 2 elliptic, inner 3 obovate   15 Merremia cordata

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