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Convolvulaceae A. L. Jussieu

旋花科 xuan hua ke

Authors: Ruizheng Fang & George Staples

Cuscuta chinensis

Credit: Harvard University Herbaria

Herbs or shrubs, usually with twining or climbing stems or erect, often with milky juice. Leaves alternate, simple, entire, dissected, or compound, absent in parasitic species. Flowers solitary, axillary or in cymes, racemes, panicles, umbels, or capitula, bisexual, actinomorphic, usually 5-merous, often showy. Sepals free, often persistent, sometimes enlarged in fruit. Corolla sympetalous, funnelform, campanulate, salverform, or urceolate; limb subentire or deeply lobed. Stamens alternating with corolla lobes, adnate to corolla; filaments filiform, equal or unequal in length; anthers introrse, laterally and longitudinally dehiscing; pollen smooth or finely spiny. Disc ringlike or cupular. Ovary superior, mostly 2-carpellate, 1- or 2-loculed, rarely 3- or 4-loculed; ovules basal, erect. Styles 1 or 2, terminal (gynobasic in Dichondra) or very short or absent; stigma entire or 2- (or 3)-lobed, rarely peltate. Fruit a capsule, dehiscing by valves, circumscissile, or irregularly shattering, less often a berry or nutlike. Seeds usually trigonous, smooth or pubescent.

About 58 genera and 1650 species: widely distributed in tropical, subtropical, and temperate regions; 20 genera and 129 species in China.

Aniseia biflora (Linnaeus) Choisy and A. stenantha (Dunn) Ling, recognized in the Fl. Reipubl. Popularis Sin., are here treated as Ipomoea biflora and I. fimbriosepala, respectively, because both have pantoporate and spinulose pollen. Strictly speaking, Aniseia is a neotropical genus of about five species, of which A. martinicensis (Jacquin) Choisy is widely naturalized as a common weed in rice paddies in Thailand and other southeast Asian countries. It will probably be found in S China eventually.

The family is important in China for food plants (Ipomoea batatas (Linnaeus) Lamarck and I. aquatica Forsskål), several ornamentals (Ipomoea), several medicinal plants (Erycibe, Ipomoea, Cuscuta, Merremia, Dichondra, Evolvulus), and numerous noxious weeds (Cuscuta, Calystegia, Convolvulus).

Fang Rhui-cheng & Huang Shu-hua in Wu Cheng-yih, ed. 1979. Convolvulaceae. Fl. Reipubl. Popularis Sin. 64(1): 1-153.

Pollen aperture type and surface ornamentation are important characters in the classification of Convolvulaceae at the generic level and above. The most critical feature of the pollen is whether the grain surface is spiny or not. This distinction separates the eight tribes recognized by Austin (Ann. Missouri Bot. Gard. 60: 306-412. 1973) into two rather cohesive groups. A low magnification (20 ) is adequate for discerning the presence or absence of minute spines on the surface.

For the successful identification of Convolvulaceae, both flowering and fruiting material should be collected. The first key to genera requires adequate fertile material with both flowers and fruit, and requires use of a pollen character. The second key may be used as an aid to identification where material is lacking flowers or fruit, but in some instances it is still partially dependent upon having both flowers and fruit.


Key 2

1 Plants parasitic, leafless, with haustoria; flowers 2-9 mm, in dense clusters or short racemes; corolla inside usually with 5 fimbriate scales opposite sepals   20 Cuscuta
+ Plants not parasitic, with well-developed leaves; inflorescences and corolla not as above (scales present in Lepistemon but entire, ± fused to filaments, flowers 10-22 mm (less than 8 mm in Poranopsis), in ± umbellate cymes).   (2)
       
2 (1) Styles 2, free or joined partway.   (3)
+ Style 1 or absent.   (5)
       
3 (2) Robust lianas; 1 bract greatly enlarged in fruit, winglike, decurrent along peduncle so fruit is inserted at center   3 Neuropeltis
+ Creeping herbs; bracts always inconspicuous.   (4)
       
4 (3) Ovary and fruit deeply 2-lobed; styles gynobasic, joined at base, unbranched   1 Dichondra
+ Ovary entire, not 2-lobed; styles terminal, free, each 2-branched   2 Evolvulus
       
5 (2) Style absent; stigma ± conical, 5-10-ridged; fruit a slightly fleshy berry, much longer than inconspicuous sepals   4 Erycibe
+ Style present, longer than stigma (usually much longer); stigma 2-lobed; fruit dry or if ± fleshy then sepals conspicuous, often brightly colored.   (6)
       
6 (5) Specimen in flower (fruit needed at couplets 15, 18).   (7)
+ Specimen in fruit (flowers needed at couplets 25, 32-36).   (21)
       
7 (6) Stigmas 2, clearly longer than wide, ovate-oblong, elliptic, oblong, clavate, cylindric, to linear.   (8)
+ Stigma 1, ca. as thick as wide, ± capitate or shallowly 2-globose (ellipsoid in Dinetus).   (11)
       
8 (7) Bracts or bracteoles prominent, sepal-like or leaflike, persistent in fruit.   (9)
+ Bracts and bracteoles inconspicuous, scalelike, linear or subulate, often deciduous.   (10)
       
9 (8) Corolla pale yellow or whitish, center purple; bracts oblong-lanceolate, attached visibly below calyx; capsule pilose   8 Hewittia
+ Corolla pinkish, lavender, or white, center often paler; bracteoles broadly ovate, sometimes saccate, closely enclosing calyx; capsule glabrous   10 Calystegia
       
10 (8) Stigmas linear, cylindric, or clavate; hairs 2-armed or simple, always present; pollen ellipsoid, 3-colpate   11 Convolvulus
+ Stigmas elliptic or oblong; hairs stellate (3- or more rayed), sometimes absent; pollen globose, usually 5-zonocolpate   9 Jacquemontia
       
11 (7) Ovary 1-locular; flowers in bracteate racemes or panicles, lower bracts often cordate.   (12)
+ Ovary 2(-4)-locular; flowers in relatively few-branched cymes, umbel-like or capitulate; bracts not cordate (except some Argyreia), often minute and/or soon falling.   (14)
       
12 (11) Herbaceous twiners; corolla glabrous outside or lobes with a minute apical tuft of hairs   7 Dinetus
+ Woody climbers; corolla pubescent outside on midpetaline bands.   (13)
       
13 (12) Flowers less than 8 mm, white, in ± crowded panicles; sepals ± equal; bracteoles minute, scalelike   5 Poranopsis
+ Flowers 10-35(-50) mm, blue, violet, or white, in racemes or few-branched panicles; sepals unequal; bracteoles sepal-like, forming a secondary calyx (calycle) immediately below calyx   6 Tridynamia
       
14 (11) Corolla urceolate; filaments dilated basally into a concave scale, scales arched over ovary   16 Lepistemon
+ Corolla campanulate, funnelform, or salverform; filaments basally pubescent or glandular, not forming scales.   (15)
       
15 (14) Leaves (and often sepals and corolla lobes) with small dark glandular dots; fruiting sepals leathery, apex rounded   19 Stictocardia
+ Leaves (sepals, corolla lobes) without glandular dots; fruiting sepals not leathery, apex often acute.   (16)
       
16 (15) Flowers solitary, nodding; corolla waxy, limb erect, subentire or shallowly 5-dentate; slender ± woody twiners (in China)   17 Blinkworthia
+ Flowers few to many in cymes or capitula; corolla mostly membranous or transparent, limb spreading or recurved, subentire, 5-lobed to deeply 5-parted; twining or trailing herbs, scandent shrubs, or lianas.   (17)
       
17 (16) Pollen spiny.   (18)
+ Pollen smooth.   (19)
       
18 (17) Fruit a fleshy, mealy, or leathery berry, indehiscent or breaking up irregularly; adaxially sepals and berry often brightly colored   18 Argyreia
+ Fruit a capsule, usually 4- (or 6)-valved, woody and seemingly indehiscent in I.aquatica; adaxially sepals and fruit green or brown   15 Ipomoea
       
19 (17) Inner 3 sepals tapering into slender points apically; leaves linear, oblong-linear, lanceolate-elliptic, or oblanceolate to spatulate, base hastate, ± clasping stem; pollen pantoporate; herbaceous, stems prostrate or tips twining   13 Xenostegia
+ Inner sepals not tapering into slender points apically; leaves variously shaped, usually wider, bases rarely clasping (except some M. hirta); pollen colpate or rugate; woody or herbaceous, often climbing, sometimes prostrate.   (20)
       
20 (19) Stems terete or striate, not winged; corolla much longer than calyx, usually yellow, less often lilac, pink, reddish, white, or white with red center   12 Merremia
+ Stems (and often petioles, peduncles) winged; corolla ca. 2 as long as calyx, white with yellow center   14 Operculina
       
21 (6) Stems (and often petioles, peduncles) winged; fruit with a thickened circumscissile lid that separates from ± papery and tardily shattering endocarp   14 Operculina
+ Stems terete or striate, not winged; fruit dehiscent or indehiscent but without a thickened circumscissile lid.   (22)
       
22 (21) Fruit indehiscent.   (23)
+ Fruit a 4- or more-valved capsule.   (29)
       
23 (22) Stems prostrate, fistulose, growing in water or in very wet situations   15 Ipomoea
+ Stems climbing or prostrate, not fistulose, growing on land.   (24)
       
24 (23) Calyx enlarged, < length of fruit; adaxial surface of sepals often brightly colored (except Blinkworthia, some Argyreia); fruit fleshy, mealy, or leathery   18 Argyreia
+ Calyx greatly enlarged, clearly longer than fruit; adaxial surface of sepals greenish or brownish; fruit papery to thinly woody.   (26)
       
25 Flowers solitary, nodding; corolla waxy, limb erect, subentire or shallowly 5-dentate; fruiting sepals ± enclosing berry, adaxially brownish   17 Blinkworthia
+ Flowers few to many in cymes or capitula; corolla membranous or transparent, limb spreading to recurved, subentire, 5-lobed, to deeply 5-parted; fruiting sepals usually reflexed from berry, adaxially often colored   18 Argyreia
       
26 (24) Leaves (and often sepals and corolla lobes) with minute blackish glandular dots abaxially; fruit with 4 or less seeds, wall at length eroding between septa, lantern-shaped   19 Stictocardia
+ Leaves (and sepals and corolla lobes) without blackish dots; fruit 1-seeded, wall not eroding and becoming lantern-shaped.   (27)
       
27 (26) Herbaceous twiners; all 5 sepals ± equally elongated in fruit or inner sepals slightly less so   7 Dinetus
+ Woody climbers; outer 2 or 3 sepals greatly elongated in fruit, inner sepals much less so.   (28)
       
28 (27) Bracteoles minute, scalelike; fruiting sepals with a single midvein and reticulate secondary veins   5 Poranopsis
+ Bracteoles sepal-like, forming a secondary calyx (calycle) immediately below calyx; fruiting sepals with 7, 9, or 11 parallel longitudinal veins   6 Tridynamia
       
29 (22) Bracts or bracteoles enlarged, surrounding capsule and sepals.   (30)
+ Bracts and bracteoles not enlarged, not surrounding calyx and capsule, sometimes deciduous.   (31)
       
30 (29) Inflorescences usually 1-flowered; each flower closely subtended by 2 leafy, often strongly convex bracteoles   10 Calystegia
+ Inflorescences with several flowers surrounded by an involucre of bracts   15 Ipomoea
       
31 (29) Capsule 8-valved (in Chinese species); hairs stellate, 3- or more rayed, rarely absent   9 Jacquemontia
+ Capsule usually 4-valved (6-valved in some Ipomoea); hairs simple or 2-armed.   (32)
       
32 (31) Stigmas linear, cylindric, clavate, or ovate-oblong and complanate.   (33)
+ Stigmas capitate, 2-globular (3-globular in some Ipomoea).   (34)
       
33 (32) Pedicel with 2 persistent leafy bracts; outer 3 sepals enlarged in fruit; corolla pale yellow or whitish, center darker; stigmas ovate-oblong, complanate   8 Hewittia
+ Pedicel without bracts or bracts minute scales; sepals not enlarged in fruit, persistent; corolla red, rose, pink, or whitish, center paler; stigmas linear, cylindric, or clavate   11 Convolvulus
       
34 (32) Pollen spiny, pantoporate.   (35)
+ Pollen smooth, 3-12-colpate, polyrugate, or pantoporate.   (36)
       
35 (34) Corolla urceolate; filaments dilated basally into a concave scale, scales arched over ovary   16 Lepistemon
+ Corolla campanulate, funnelform, or salverform; filaments basally pubescent, glandular, or glabrous, not dilated into scales   15 Ipomoea
       
36 (34) Herbs prostrate, tips often twining; inner 3 sepals tapering into slender points apically; leaf bases hastate, basal lobes dentate; pollen pantoporate   13 Xenostegia
+ Herbs twining or prostrate, or woody climbers; inner 3 sepals not tapering into points apically; leaf bases not as above; pollen 3-12-colpate or polyrugate   12 Merremia

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