M.T.M. RAJPUT & S.S. TAHIR
Cuscuta planiflora Ten.
Stem thin to medium, light to dark. brown, usually not interlaced. Leaves minute, scarious to fleshy, oblong to triangular, 1-2 x 0.3-2 mm, or sometime obsolete. Flowers sessile or pedicelate, arranged in loose to compact glomerules, usually subtended by narrow triangular bracts, each cluster having 8-22 flowers, 1.5-3.2 mm long; bracts leaf-like; pedicel 0.5-2 mm long; calyx lobes 5, rarely 4 or 6, mostly unequal, ovate, oblong-elliptical or spathulate, usually reticulate, thick, fleshy, tips mostly thick and having folds with some glandular substance, acute-obtuse, slightly overlapping in the middle, 1.5-3 x 0.5-2 mm; connate part of the sepal lobes 0.5-2 mm long. Corolla campanulate, becoming urceolate as the fruit develops; Petals mostly 5, rarely 4 or 6, brown, oblong, oblong-elliptical or ovate, obtuse or acute-obtuse, telexed, usually lower half membranous, upper half thick; corolla tube 1.2-1.5 mm long; scales memberanous, equal or slightly bigger than corolla tube, slightly fringed, 0.5-1.5 mm long. Stamens 5, rarely 4 or 6, equal to or longer than corolla tube; filament linear-oblong, broader at the base narrowing towards apex, fused part of the filament not prominent, 0.3-0.5 x 0.2-0.4 mm. Ovary globular, fleshy, brown, 0.5-1.5 x 1.5-2.5 mm; styles 2, linear, c. 1 mm long, stigmas 2, linear, reddish to purple, 0.4-1.2 mm long; ovales mostly 4, triangular or ovoid, light brown with brown with papillate pattern, 1-1.2 x 0.5-1 mm. Capsule globose-conical to depressed, with a intrastylar opening, enveloped with a withered corolla, circumscissile with a definite line of cleavage, 1.5-2.2 x 2-2.5 mm. Seeds mostly 4 rarely 3, compressed, slightly angled, triangular ovoid or irregularly ovoid, hilum oblong, transverse with a slightly brown area around it.
Type: Described from Europe, Herb. Linn. 170/1 (LINN).
Hosts: Artemisia, Lactuca orientalis, Convolvulus, Alhagi, Sambucus, Cannabis, Anagallis, Otostegla limbata, Sonchus, Heliotropium, Medicago, Indigofena, Thymus, Plectranthus and Trigonella.
Yuncker and many other workers separated Cuscuta approximate from Cuscuta europaea mainly on the basis of capsule Character, i.e. depressed in Cuscuta approximate and conical in Cuscuta europaea. However there is a remarkable variation in the depression of the capsule, size of the petals, and shape of the scales, number of the flowers in the clusters, size of the pedicel. We have examineds more than 200 specimens including a few specimens from A, BM, E, K, MICH, O and E which were previously identified as Cuscuta europaea and Cuscuta approximate. But in our opinion it is not possible to separate Cuscuta europaea from Cuscuta approximate.
Tutin, l.c., separated Cuscuta approximate by having the calyx tube golden-yellow, shiny, and reticulate. But there is continuous variation of these characters. Plitmann, l.c., separated Cuscuta europaea from Cuscuta approximate by the presence of usually 4-merous flowers, style and stigmas shorter than ovary whereas in the latter taxon the flowers are infrequently 4-5 merous, the stigma and style usually longer or rarely shorter than ovary. A remarkable variation is found in the number of petals and sepal lobes: mostly flowers have 5 petal and sepal lobes, but a few flowers, even from the same cluster, have 4 or 6 petal and sepal lobes. Variation also exists in the colour, size and degree of bending of the style and. stigma. In the specimens we have examined the character combination used by Plitmann to separate Cuscuta approximate and Cuscuta europaea breaks down, and these two taxa cannot be recognized as two distinct species.
We have examined the type specimen of Cuscuta kotschyana [S. Persia, Kuh-Daena, Kotschy 749, (G, O!)] and could not find any reasonable difference between it and Cuscuta europaea. As mentioned above there is a wide range of varialion within Cuscuta europaea. The characters of the type specimen of Cuscuta kotschyana fit well within the variation range of Cuscuta europaea.
We have also examined specimens of Cuscuta planijlora Tenore, and are unable to find any significant differences between it and Cuscuta europaea; the only minor difference we have noticed is that in Cuscuta planifora the flowers are slightly more compactly arranged in clusters than in Cuscuta europaea. Engehnan also considered; Cuscuta planifora and Cuscuta approximate to be conspecific.
Cuscuta brevistyla A. Braun. ex A. Rich, is also not recognized as a separate species. Yuncker 1932 & 1964, mentioned in his descriptions of Cuscuta brevistyla that "considerable variation is observed in this species which in many of its characters resembles Cuscuta approximate (synonym of Cuscuta europaea) and Cuscuta planiflora”. He had separated Cuscuta brevistyla from Cuscuta approximate and Cuscuta planiflora on the basis short style and less turgid perianth parts. However, these characters do not apperar to be significant enough to separate the taxa. Most probably previous taxonomists have separated Cuscuta brevistyla from Cuscuta europaea because of the small number of collections available to them.