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RH 834 Wadi Dhar, YEMEN
Origin and Habitat: Saudi Arabia, Yemen, Oman. In Oman this species reaches its easternmost occurrence.
Habitat and ecology. Caralluma hexagona grows in rocky habitats, usually in shallow soil in crevices between large stones or in rock outcrops. The greyish colour of the inner surface of the outer corona-lobes presumably caused by the secretion of nectar which rapidly dries out to form a thin, crystalline deposit, coupled with the evil, dung-like odour of the flowers and the clavate cilia that are often present on the margins towards the end of the corolla-lobes, acts as an attractant for the pollinators of these flowers.
- Caralluma hexagona Lavranos
Caralluma hexagona Lavranos
J. S. African Bot. 29: 105 1963.
- Caralluma hexagona Lavranos
- Caralluma foulcheri-delboscii Lavranos
- Sulcolluma foulcheri-delboscii (Lavranos) Plowes
- Caralluma foulcheri-delboscii var. greenbergiana Lavranos
- Sulcolluma foulcheri-delboscii var. greenbergiana (Lavranos) Plowes
- Caralluma hexagona var. septentrionalis Lavranos & L.E.Newton
- Sulcolluma hexagona var. septentrionalis (Lavranos & L.E.Newton) Plowes
- Caralluma shadhbana Lavranos
- Sulcolluma shadhbana (Lavranos) Plowes
- Caralluma shadhbana var. barhana Lavranos & L.E.Newton
- Sulcolluma shadhbana var. barhana (Lavranos & L.E.Newton) Plowes
Description: Caralluma hexagona is an upright or ascending, strongly branching, succulent. It forms dense mats or clumps to 20 cm tall, with subterranean runners. It is a well-worth growing because of its tiny but interesting flowers with marginal purple hairs (not always present) that wave in the slightest breeze. It is an extremely variable species, which can possibly be split up into several taxa that have proved rather difficult to identify. Plants from Saudi Arabia does not fit well into the concepts of the species described from North Yemen and further south. Similarly, collections from Oman, and further west in the Yemen Arab Republic (North Yemen), differ sufficiently that doubt as to their identity exists.
Stems: Grey-green or green, 3 - 5 (-8) cm long, 1.5 - 2 cm thick, bluntly 4-ribbed.
Ribs: Flattened, undulate-dentate. Tubercles oblong, slightly spreading, apically with hard scar-tissue.
Inflorescences: 5- to 15- (to 20-) flowered. Peduncle short, long-tapering. Bracts short, linear. Pedicels green, 4-10 mm long, 1.5-3 mm wide.
Flowers: Sepals finely dotted with red, 1-3 long, about 1 mm wide, deltoid or linear, acute. Corolla outside greenish-white, densely dotted with red, dots small, convex, inside greenish or cream-coloured, densely dotted with purplish-red, 2.2 cm in diameter, flat or campanulate. Corolla-tube, 4 x 6 mm long, enclosing or just basally encircling the corona. Corolla-lobes triangular, 8 mm long, margins slightly revolute, inside tuberculate, lobes apically hairy, hairs dark purple, seed 2 mm, simple, compressed, vibratile. Corona 6 mm in diameter. Outer corona-lobes pale red, brownish-purple to bluish, margins pink, basally white, lobes 1.5 mm long, deeply bifid, curved outwards, appendages of neighbouring lobes sometimes overlapping, with distinct furrows median and in the area where fused with the inner-corona. Inner-corona pale red or pink, apically yellowish, lobes about 1 mm long, lanceolate to ribbon-like, apically tapering, obtuse, strongly broadened in the area where fused with the outert corona; Anthers 0.5 mm broad, apically ovoid.
Related species: Caralluma hexagona is a close relative of the tall growing Caralluma awdeliana, Caralluma petraea and Caralluma arabica and does not seem to be especially closely allied to Caralluma europaea, which has a similar mat-forming habit.
Subspecies, varieties, forms and cultivars of plants belonging to the Carallum exagona group
Caralluma hexagona is extremely variable, three species and three varieties have been described but plants with intermediate or not typical characteristics occur at random in each populations, and often within a single population both flat and campanulate flowers will sometimes be found. Nor the shape and colour of the corolla-lobes is sufficient to distinguish without ambiguity between species. The number of ribs varies from 4 to 6, but seems to be unreliable in certain groups, and is therefore of little use in separating these taxa. It appears that there is inherently a large range of variation in many of the features of these plants and it is possible that this is brought about by highly localized modifications of the very harsh environment in which they occur.
- Caralluma foulcheri-delboscii Lavranos: C. has less robust, ascending stems, usually 4-angled and the flowers are rather small, with relatively deep corolla-tube and ascending corolla- and outer corona-lobes. Distribution: Hadramawt region, South Yemen
- Caralluma foulcheri-delboscii var. greenbergiana Lavranos: Distribution: Near Mukayras, South Yemen.
- Caralluma hexagona Lavranos: (var. exagona) has 4-6 angled, sturdy, usually creeping stems and fairly large flowers. Distribution: Near Al Madhan, South Yemen.
- Caralluma hexagona var. septentrionalis Lavranos & L.E.Newton: Distribution: Near Sana'a in North Yemen
- Caralluma shadhbana Lavranos: has stems slender and 4-angled. Flowers with ovate-deltoid corolla-lobes, are dark purple or yellow-green with purple-brown dots. Distribution: Near Manakhah, North Yemen.
- Caralluma shadhbana var. barhana Lavranos & L.E.Newton: Distribution: 50km west of Ta'izz in North Yemen.
Bibliography: Major references and further lectures
1) Focke Albers, Ulrich Meve “Illustrated Handbook of Succulent Plants: Asclepiadaceae: Asclepiadaceae” Volume 4 Springer, 2002
2) Plowes, D. (1995). “A reclassification of Caralluma R. Br. (Stepelieae: Asclepiadaceae)”. Haselotnia 3: 49–70.
3) Cactus and Succulent Journal, Volume 47 1975
4) P. V. Bruyns “Miscellaneous notes on Stapelieae (Asclepiadaceae)- A note on Caralluma hexagona Lavranos” Bradleya, volume 5, pp. 87-89, 1987
5) Caralluma hexagona Lavranos in J. S. Afr. Bot. 29:105 (1963)
6) Caralluma shadhbana Lavranos in Flow. PI. Afr. 44(3): t.1743 (1977)
7) Caralluma foulcheri-delboscii var. greenbergiana Lavranos in Cact. Succ. J. (US) 39(1): 6 (1967)
Cultivation and Propagation: Caralluma hexagona is quite difficult to grow and propagate.
Propagation: It is rooted from side-branches.
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