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.
Cycas hongheensis was firstly proposed as a distinct taxon in 1994 and formally described two years later based on vegetative materials only. Here, the reproductive organs of this species, namely, the female cone, male cone and seeds are supplemented for description as these fertile materials were found for the first time at the type locality. Furthermore, the phylogenetic position of this species as being the only endemic member of Cycas sect.
Cycas hongheensis S. Y. Yang & S. L. Yang ex D. Y. Wang in F. X. Wang et al., Cycads in China. 62. 1996.
灰干苏铁 hui gan su tie
Trunk cylindric, sometimes branched, to 8 m × 60 cm, apex not tomentose; bark gray, smooth toward base of trunk, with fine, longitudinal fissures. Leaves 20-50(-60), 1-pinnate, 50-120 × 15-35 cm; petiole subterete, 10-25 cm, with 25-50 spines along each side; leaf blade oblong to elliptic-lanceolate, strongly "V"-shaped in cross section, recurved, pale brown tomentose when young; leaflets in 50-70 pairs, horizontally inserted at 45-50° above middle of rachis, glaucous when mature, 8-18 cm × 6-8 mm, leathery, densely pubescent when young, midvein flat adaxially when fresh (but sulcate when dry), prominent abaxially, base decurrent, margin ± revolute, apex
acuminate, pungent. Cataphylls lanceolate, 3-5 × 1-1.5 cm, densely pale brown tomentose adaxially, apex acuminate, pungent. Pollen cones and megasporophylls unknown.
* Dry and hot, sunny forests with sparse trees on sharp limestone slopes; 400-600 m. SE Yunnan (Gejiu Shi).
Very rapidly disappearing in the wild as a result of over collec-tion by commercial dealers and habitat destruction; it should be con-sidered an endangered species in China. There is no doubt as to the distinctiveness of this species on the basis of vegetative characters, although its affinities are difficult to ascertain in the absence of fertile material.
Taken from
http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=210000343
