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FOC | Family List | FOC Vol. 16 | Convolvulaceae

20. Cuscuta Linnaeus, Sp. Pl. 1: 124. 1753.

菟丝子属 tu si zi shu

Fang Rhui-cheng; Lytton J. Musselman, Uzi Plitmann

Cuscuta chinensis

Credit: Harvard University Herbaria

Herbs parasitic, yellow or reddish, glabrous. Stems twining, filiform, obtaining nourishment from hosts by haustoria. Leaves reduced to minute scales. Flowers sessile or short pedicellate, mostly in globular, spicate, racemose, or cymose clusters, 4- or 5-merous; bracts minute or absent. Calyx gamosepalous, ± deeply lobed, or sepals free. Corolla white, pinkish, or cream colored, urceolate, tubular, globose or campanulate, inside with fimbriate or crenulate, membranous, infrastaminal scales at base of tube. Stamens as many as corolla lobes, inserted on corolla above scales, alternating with corolla lobes. Pollen smooth. Ovary 2-loculed; ovules 2 per locule. Styles 1 or 2; stigmas 2, subglobose or elongated, sometimes united. Capsule ovoid or globose, dry or sometimes fleshy, circumscissile or opening irregularly. Seeds 1-4, glabrous; embryo acotyledonous, filiform spiral-curved.

About 170 species: mainly in North and South America, several in Asia and Europe; 11 species in China.

Cuscuta is placed by some in a separate family, Cuscutaceae Dumortier.

The following article appeared after publication of the treatment, and may be useful for better understanding floral variations: Liao, G.-I., C.-S. Kuoh & M.-Y. Chen. 2005. Morphological observation on floral variations of the genus Cuscuta in Taiwan. Taiwania 50: 123–130. 2005.

1 Styles 2, distinctly elongated; inflorescences compact cymose umbellules or glomerules; stems filiform; often parasitic on herbs.   (2)
+ Style 1, or very short to absent; inflorescences racemose or spicate; stems stringy; often parasitic on shrubs.   (6)
2 (1) Stigmas clavate, ± elongated.   (3)
+ Stigmas globose or capitate, not elongated.   (4)
3 (2) Flowers short pedicellate; sepals not thickened abaxially; style and stigmas much shorter than ovary   10 Cuscuta europaea
+ Flowers sessile; sepals thickened and fleshy abaxially; style and stigmas ca. as long as or longer than ovary   11 Cuscuta approximata
4 (2) Capsule entirely enclosed by withered corolla, circumscissile; corolla lobes keeled   3 Cuscuta chinensis
+ Capsule subtended by withered corolla, irregularly dehiscent; corolla lobes flat.   (5)
5 (4) Corolla lobes ovate or oblong, apex obtuse to rounded, often erect; corolla scales less than 1/2 as long as tube, deeply 2-cleft   1 Cuscuta australis
+ Corolla lobes broadly triangular, apex acute or obtuse, often reflexed; corolla scales ca. as long as corolla tube, reaching throat, deeply fimbriate   2 Cuscuta campestris
6 (1) Style distinctly longer than stamens; stigma 2-lobed.   (7)
+ Style very short or obsolete; stigma capitate or ligulate.   (8)
7 (6) Stigma lobes elongated or ± square   4 Cuscuta japonica
+ Stigma oval, slightly lobed, lobes ovate   5 Cuscuta lupuliformis
8 (6) Corolla scales nearly reaching throat   9 Cuscuta macrolepis
+ Corolla scales reaching middle of tube.   (9)
9 (8) Stigma capitate, shallowly cleft   6 Cuscuta monogyna
+ Stigma ligulate.   (10)
10 (9) Corolla tube more than 2 as long as calyx   7 Cuscuta reflexa
+ Corolla tube to 2 as long as calyx   8 Cuscuta gigantea

  • List of lower taxa


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