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The Cycad Pages
Cycas tansachana

Cycas tansachana K.D. Hill & S.L. Yang, Brittonia 51(1): 65-66 (1999). H—NSW
"TYPE: Thailand, Saraburi, hills NE of Khong Khi Sua, K.D. Hill & Poonsak Vatcharakorn, 3 Mar 1997 (holo NSW; iso BKF, K, L, PE)."


Photo Ken Hill
Etymology: Honouring Kampon Tansacha, of the Nong nooch Tropical Gardens, Thailand.

Literature: Tang et al. 1997.

Illustrations: Tang et al. 1997

Historical notes: Discovered in 1995.

Distinguishing features: This species is similar to C. clivicola in many respects, differing in the larger and distinctly keeled leaves with stiffer, broader leaflets, and the larger male cones, megasporophylls and seeds. The bark is also somewhat thicker and more corky, and the crown of orange wool around newly developed cataphylls is not seen in any other Thai species or in any other species in the C. pectinata group.

Distribution and habitat: Known only from limestone outcrops near Saraburi, growing in full sun or part shade in crevices in bare rock.

Conservation status: Apparently quite restricted in occurrence and under severe pressure from plant collectors and limestone mining operations, this species should be regarded as highly threatened. IUCN (1994) Red List status CR A2c,B2.
Photo Ken Hill
Photo Ken Hill

Description:

Stems arborescent, to 2-5 m tall, 10-18 cm diam. at narrowest point; 24-60 leaves in crown.

Leaves deep green, semiglossy, 100-180 cm long, moderately keeled (opposing leaflets inserted at 90-140° on rachis), with 130-200 leaflets, with white tomentum shedding as leaf expands; rachis frequently terminated by a spine 1-3 mm long. Petiole 30-45 cm long (20-30% of total leaf), petiole glabrous, unarmed or spinescent for 0-30% of length. Basal leaflets not gradually reducing to spines, 80-160 mm long.

Median leaflets simple, strongly discolorous, 170-300 mm long, 8-12.5 mm wide, inserted at 60-70° to rachis, decurrent for 3-5 mm, narrowed to 2.5-4 mm at base (to 25-45% of maximum width), 10-17 mm apart on rachis; median leaflets section flat; margins slightly recurved; apex acute, not spinescent; midrib flat above to raised above (slightly), raised below.

Cataphylls narrowly triangular, soft, pilose, 50-60 mm long, persistent.

Pollen cones narrowly ovoid, yellow, 25-45 cm long, 11-13 cm diam.; microsporophyll lamina firm, not dorsiventrally thickened, 33-45 mm long, 12-15 mm wide, fertile zone 27-40 mm long, sterile apex 6-15 mm long, level, apical spine prominent, sharply upturned, 1-3 mm long.

Megasporophylls 20-22 cm long, yellow-tomentose to brown-tomentose; ovules 2-4, glabrous; lamina orbicular, 100-140 mm long, 60-70 mm wide, deeply pectinate, with 40-60 soft lateral spines 18-25 mm long, 1-1.5 mm wide, apical spine distinct from lateral spines, 30-50 mm long, 5-7 mm wide at base.

Seeds flattened-ovoid, 45-50 mm long, 35-40 mm wide; sarcotesta yellow, not pruinose, 4 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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