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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 1

1 Plants parasitic, leafless, with haustoria; flowers in clusters or short racemes; corolla inside usually with 5 fimbriate scales opposite sepals   20 Cuscuta
+ Plants not parasitic, with green leaves; flowers and corolla not as above (scales present in Lepistemon but flowers in ± umbellate cymes).   (2)
       
2 (1) Pollen pantoporate, finely spiny.   (3)
+ Pollen grains with various aperture types, never finely spiny.   (7)
       
3 (2) Fruit dehiscing by 4 (or more) valves, sometimes tardily so.   (4)
+ Fruit indehiscent, or at length eroding or irregularly breaking open.   (5)
       
4 (3) 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 Ipomoea
       
5 (3) Calyx greatly enlarged, completely enclosing fruit; leaves (and often sepals and corolla lobes) with minute blackish glandular dots abaxially; fruit wall at length eroding between septa, lantern-shaped   19 Stictocardia
+ Calyx enlarged, either reflexed from fruit or not fully enclosing it; leaves (and sepals and corolla lobes) without blackish dots; fruit an indehiscent or irregularly shattering berry.   (6)
       
6 (5) Flowers few to many in cymes or capitula; corolla mostly membranous or transparent, limb spreading to recurved, subentire, 5-lobed to deeply 5-parted; twining or trailing herbs, scandent shrubs, or lianas; sepals usually reflexed from fruit, often colored adaxially   18 Argyreia
+ Flowers solitary, nodding; corolla waxy, limb erect, subentire or shallowly 5-dentate; slender woody twiners (in China); sepals ± enclosing fruit   17 Blinkworthia
       
7 (2) Ovary deeply 2-lobed; styles 2, gynobasic   1 Dichondra
+ Ovary not deeply 2-lobed; styles, if present, terminal.   (8)
       
8 (7) Styles absent; stigma 1, ± conical, 5-10-ridged; corolla deeply 5-lobed, each lobe 2-lobulate apically   4 Erycibe
+ Styles present, sometimes very short; neither stigma nor corolla as above.   (9)
       
9 (8) Outer 2 or 3 or all 5 sepals much enlarged in fruit and falling off with fruit as a dispersal unit; fruit indehiscent; seeds 1.   (10)
+ Sepals enlarged in fruit or not, remaining attached to pedicel when fruit dehisces; fruit dehiscent by valves or breaking irregularly; seeds usually 4 (or less by abortion).   (12)
       
10 (9) Herbaceous twiners; corolla glabrous outside or lobes with a minute apical tuft of hairs; all 5 sepals ± equally elongated in fruit or inner sepals slightly less so   7 Dinetus
+ Woody climbers; corolla pubescent outside on midpetaline bands; outer 2 or 3 sepals greatly elongated in fruit, inner sepals much less so.   (11)
       
11 (10) Flowers mostly less than 8 mm, white, in ± crowded panicles; bracteoles minute, scalelike; fruiting sepals with a single midvein and reticulate secondary veins   5 Poranopsis
+ Flowers 10-35(-50) mm, blue, violet, or white, in racemes or few-branched panicles; bracteoles sepal-like, forming a secondary calyx (calycle) immediately below calyx; fruiting sepals with 7, 9, or 11 parallel longitudinal veins   6 Tridynamia
       
12 (9) Styles 2, free or united basally.   (13)
+ Style 1, entire or with 2 minute branches concealed by stigmas.   (14)
       
13 (12) Plants erect or sprawling, never twining; bracts tiny, not enlarged in fruit; styles 2-cleft; stigmas terete, filiform or slightly clavate   2 Evolvulus
+ Plants climbing; 1 bract greatly enlarged, winglike in fruit; styles entire; stigmas peltate or reniform, rather deeply lobed   3 Neuropeltis
       
14 (12) Stigmas ± globular; calyx enlarged in fruit, often enclosing it.   (15)
+ Stigmas elliptic, ovate-oblong, oblong, ovate, or linear, usually ± flattened; calyx not enlarged in fruit or outer 3 sepals somewhat enlarged, inner sepals less so.   (17)
       
15 (14) Herbs prostrate; leaves linear, oblong-linear, lanceolate-elliptic, or oblanceolate to spatulate, base hastate, ± clasping stem; inner 3 sepals tapering into slender points apically; pollen pantoporate   13 Xenostegia
+ Herbs twining or woody climbers (sometimes prostrate); leaves variously shaped, usually wider, bases rarely clasping (except some Merremia hirta); inner sepals tapering into slender points apically; pollen colpate or rugate.   (16)
       
16 (15) Stems terete or striate, not winged; fruit a 4-valved capsule or shattering irregularly   12 Merremia
+ Stems (and often petioles, peduncles) winged; fruit with a thickened circumscissile lid that separates from ± papery and tardily shattering endocarp   14 Operculina
       
17 (14) Bracts or bracteoles prominent, sepal-like or leaflike, persistent in fruit.   (18)
+ Bracts inconspicuous, scalelike, linear or subulate, deciduous or persistent in fruit.   (19)
       
18 (17) 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 sepal-like, broadly ovate or elliptic, attached just below and closely enclosing calyx; capsule glabrous   10 Calystegia
       
19 (17) Stigmas linear or clavate; hairs 2-armed or simple; pollen ellipsoid, 3-colpate   11 Convolvulus
+ Stigmas elliptic or oblong; hairs stellate (3- or more armed); pollen globose, usually 5-zonocolpate   9 Jacquemontia

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