Photo Ken Hill
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The Cycad Pages
Cycas chamaoensis

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]


Etymology: From the mountain of Khao Chamao, the type locality and the only known habitat of this species.

Historical notes: Discovered in 1994 and formally described in 1999.

Distinguishing features: 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 rock slopes.

Conservation status: 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

Description:

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.


The Cycad Pages

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Written and maintained by Ken Hill 1998-2010
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