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Etymology:
From Honghe (the Red River), near the habitat in south-eastern Yunnan, with
the Latin suffix -ensis, place of origin.
Literature: Chen & Stevenson 1999, Chen & Stevenson 1999
Illustrations: Wang 1996,
Historical notes: This member of the C. pectinata group was first discovered and noted as a distinct taxon by Chinese botanists in 1984, although no reproductive material was seen. It was finally described in 1996, still in the absence of reproductive material.
Distinguishing features: The heavy cutting of the known plants by local villagers for trade has blocked reproduction for many years, and reproductive structures of this species remain unknown. A few seeds observed in the markets were of the C. pectinata type (S.L. Yang pers. comm.), and the the tall, smooth trunk is quite similar to that of C. pectinata and related species from Thailand. The keeled, bluish leaves with a moderately persistent white tomentum distinguish it immediately from all other species in the C. pectinata group.
Distribution and habitat: Known from only a few populations in the Hong He river valley in the west of Gejiu county. Once locally common on steep limestone outcrops at lower elevations, but now severely depleted by collecting for sale as an ornamental plant. Plants are in low open vine thickets, often with succulent Euphorbia species, and most often rooted in clefts and crevices, often with little no soil at the roots. This species is apparently endemic to these seasonally dry limestone outcrops.
Conservation status: Known populations have been very heavily cut for sale as ornamentals, killing many plants and blocking reproduction in survivors. 1994 IUCN Red List of Threatened Plants category CR.
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Stems arborescent, to 1-3 m tall, 12-15 cm diam. at narrowest point; 12-25 leaves in crown.
Leaves grey-green, dull, 70-100 cm long, strongly to moderately keeled (opposing leaflets inserted at 80-120° on rachis), with 120-140 leaflets, with white tomentum persistent above and below; rachis usually terminated by a spine 5 mm long. Petiole 26 cm long (30% of total leaf), petiole pubescent, spinescent for 100% of length. Basal leaflets not gradually reducing to spines, 95 mm long.
Median leaflets simple, strongly discolorous, 150-200 mm long, 7-8 mm wide, inserted at 50° to rachis, decurrent for 4 mm, narrowed to 4.5 mm at base (to 60% of maximum width), 10 mm apart on rachis; median leaflets section slightly keeled; margins slightly recurved to recurved; apex acute, not spinescent; midrib flat above or raised above (slightly), raised below.
Cataphylls narrowly triangular, pungent, thinly sericeous or lacking tomentum, 35-50 mm long, persistent.
Cones not seen.
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