|The Cycad Pages
- Cycas hoabinhensis K.L. Phan & T.H. Nguyen, "Bot. Rev. 70(2): 153-155, fig. 5" (2004). H—HNU
- "TYPE: Vietnam: Hoa Binh, Lac Thuy, Chi Ne, Jul 1966, K.L. Phan P3194a (holo HNU, iso HN, NSW)."
From the occurrence in Hoa Binh province, northern Vietnam, with the Latin
termination -ensis, place of origin.
Historical notes: Although an abundant species occuring naturally
near the large city of Hanoi and very popular as a horticulatural subject
in that city in recent years, this was not recognised as a distinct
species until 1996-8 when field studies became possible and the true
complexity of the taxonomy of the northern Vietnamese cycads
began to be appreciated.
Within a complex of closely related mostly acaulescent taxa (Section
Stangerioides), this species is distinguished by the very small
stature, small megasporophylls and the slender apical spine on the
microsporophyll. It is nearest to C. chevalieri and
C. brachycantha, both of which share the small megasporophyll
but are otherwise larger in stature. Older plants develop a short, very
slender, often twisted or decumbent aerial trunk.
Distribution and habitat:
Locally abundant, in somewhat sheltered sites on steep limestone outcrops,
usually within the canopy of closed evergreen forest on ridge crests in the
region south of Hanoi, apparently endemic in Vietnam. The habitat
is the same as that of the closely related
C. brachycantha from north of Hanoi.
This species has been extensively exploited for the ornamental plant trade
in Hanoi, severely depleting many of the more accessible populations. Although
large populations remain in relatively inaccessible areas, the extensive
depletion to date is cause for concern, and this species must be regarded as
threatened. IUCN (1994) Red List status EN A2c.
Stems arborescent or acaulescent, to 0.6 m tall, 5-8 cm diam. at narrowest point; 2-10 leaves in crown.
Leaves bright green, highly glossy, 50-130 cm long, flat (not keeled) in section (opposing leaflets inserted at 170-180° on rachis), with 40-100 leaflets, with white tomentum shedding as leaf expands; rachis consistently terminated by paired leaflets. Petiole 25-60 cm long (40-60% of total leaf), petiole glabrous, spinescent for 100% of length. Basal leaflets not gradually reducing to spines, 150-250 mm long.
Median leaflets simple, strongly discolorous, 200-280 mm long, 11-21 mm wide, inserted at 60-80° to rachis, decurrent for 2-4 mm, narrowed to 2.5-5 mm at base (to 15-30% of maximum width), 15-20 mm apart on rachis; median leaflets section flat; margins flat or undulate; apex softly acuminate, not spinescent; midrib raised above, raised below.
Cataphylls narrowly triangular, soft, pilose, 50-70 mm long, articulated.
Pollen cones narrowly ovoid or fusiform, yellow, 10-12 cm long, 5-6 cm diam.; microsporophyll lamina soft, not dorsiventrally thickened, 22 mm long, 10 mm wide, fertile zone 20 mm long, sterile apex 2 mm long, raised, apical spine prominent or rudimentary, sharply upturned, 4-10 mm long.
Megasporophylls 7 cm long, brown-tomentose; ovules 2-4, glabrous; lamina orbicular, 30 mm long, 20 mm wide, deeply pectinate, with 10 soft lateral spines 20 mm long, 2.5 mm wide, apical spine not distinct from lateral spines.
Seeds ovoid, sarcotesta yellow, not pruinose; fibrous layer absent; sclerotesta verrucose. Spongy endocarp absent.