M.T.M. RAJPUT & S.S. TAHIR
Department of Botany, University of Sindh, Jamshoro.
Twining herbaceous parasites. Stem slender, yellowish-brown or reddish-purple or with violet spots, attached to host by haustoria; spirally twining round the host, sometimes interlaced. Leaves reduced to small membranous scales. Flowers small, white to yellowish white or with violet spots usually arranged in cymose clusters or umbel-like cymes. Sepals mostly fleshy, gamosepalous, 4-5 (-6) lobed. Corolla tubular, 4-5 (-6) lobed, often with minute scales. Scales membranous or petaloid, equalling the number of stamens, attached to the corolla tube below each filament, simple or bind, filmbriate dentate or fimbriate-ciliate, forming a fringed or fimbriate ring-like structure inside the corolla tube. Stamens sessile or with filament, 5(-4), inserted in the throat, alternating with the corolla lobes. Ovary 2-locular, ovules 2 in each locule; style 1-2, free or united or obsolete; stigmas capitate or linear-elongated or oblong. Fruit a capsule, with or without intrastylar opening, 4-seeded or less by abortion, remaining closed or opening with a definite or irregular line of circumscission near its base. Embryo without cotyledons.
The genus Cuscuta L. is often placed in the family Convolvulaceae. However Dumortier (Anal. Fam. Pl. 20, 25. 1829) erected a separate family Cuscutaceae and this arangement has been followed by Hutchinson (Fam. Fl. Pl. 1: 501. 1926), Takhtajan (Fl. Pl. Orig. & Diap. 231. 1969), Cronquist (Evol. & Class. of Fl. Pl. 289. 1970) and Dahlgren (in Nord. J. Bot. 3: 119-149. 1983).
The family includes a single cosmopolitan genus Cuscuta, which has about 170 species, several of which are important weeds of agricultural crops. Represented by 14 species in Pakistan. Taxonomically a very complex genus requiring. further study.
Acknowledgements: We are thankful to the Directors/Curators of the following herbaria for the loan of herbarium specimens: BM, E, ISL, K, KUH, MICH, NY, O, PESH, RAW and SUH. We would also like to thank Mr. I.C. Hedge of Royal Botanic Garden, Edinburgh and Prof. Dr. L. J. Musselman, Department of Biological Science, Old Dominion University, Norfolk, Virginia, U.S.A. for going through the manuscript and offering valuable suggestions. The financial assistance received from United States Department of Agriculture under PL-480 programme with the coordination of Pakistan Agricultural Research Council, Islamabad, is thankfully acknowledged.