|Photo Ken Hill
|The Cycad Pages
- Cycas chamaoensis K.D. Hill, "Brittonia 51(1): 58, fig. 6" (1999). H—NSW
- "TYPE: Thailand, Khao Chamao, steep NW slopes, K.D. Hill 4617 & Poonsak Vatcharakorn, 16 Apr 1994 (holo NSW; iso BKF, K, L, PE)."[NSW]
From the mountain of Khao Chamao, the type locality
and the only known habitat of this species.
Discovered in 1994 and formally described in 1999.
this species is similar to the
true C. pectinata in most respects, differing mainly in
the narrower male cones with very much reduced spines on the microsporophylls.
The large megasporophylls with a very strongly dilated lamina
distinguish both from C. clivicola and related species,
and C. siamensis. The latter is also distinguished by its
thickened bark, together with C. takfa.
Distribution and habitat:
only known from granite outcrops
of Khao Chamao (c. 12°57'N 101°43'E), north-east of
Klaeng in Rayong, Thailand. Also common in gardens in
that area. This species grows in full sun in crevices in bare
apparently quite restricted in occurrence
and under severe pressure from plant collectors, populations of
this species have been severely depleted in recent decades, and it
should be regarded as a highly threatened species.
IUCN (1994) Red List
status CR B2.
|Photo Ken Hill
Stems arborescent, to 10 m tall, 14-28 cm diam. at narrowest point; 50-120 leaves in crown.
Leaves deep green or grey-green, semiglossy, 125-255 cm long, flat (not keeled) in section (opposing leaflets inserted at 160-180° on rachis), with 170-310 leaflets, with white tomentum shedding as leaf expands; rachis usually terminated by a spine 7-33 mm long. Petiole 30-60 cm long (20-35% of total leaf), petiole glabrous, spinescent for 0-30% of length. Basal leaflets not gradually reducing to spines, 60-140 mm long.
Median leaflets simple, strongly discolorous, 160-300 mm long, 7-11 mm wide, inserted at 60-70° to rachis, decurrent for 4-9 mm, narrowed to 2.5-3.5 mm at base (to 25-35% of maximum width), 9-14 mm apart on rachis; median leaflets section flat; margins slightly recurved; apex acute, spinescent; midrib raised above, raised below.
Cataphylls narrowly triangular, soft, pilose, articulated.
Pollen cones narrowly ovoid to fusiform, orange, 50-60 cm long, 12-13 cm diam.; microsporophyll lamina firm, not dorsiventrally thickened, 41-55 mm long, 25-30 mm wide, fertile zone 33-46 mm long, sterile apex 6-9 mm long, level, apical spine prominent, sharply upturned, 4-12 mm long.
Megasporophylls 13-18 cm long, yellow-tomentose to grey-tomentose; ovules 2-4, glabrous; lamina orbicular, 60-90 mm long, 60-90 mm wide, deeply pectinate, with 30-40 soft lateral spines 20-30 mm long, 2-3 mm wide, apical spine distinct from lateral spines, 27-35 mm long, 3-6 mm wide at base.
Seeds flattened-ovoid, 35-40 mm long, 30-40 mm wide; sarcotesta yellow, not pruinose, 3 mm thick; fibrous layer present; sclerotesta smooth. Spongy endocarp absent.