Photo P.K. Loc
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The Cycad Pages
Cycas tropophylla

Cycas tropophylla K.D. Hill & S.L. Yang, "Bot. Rev. 70(2): 168-170, fig. 10" (2004). H—HN
"TYPE: Vietnam: Quang Ninh: island in Ha Long Bay (21°50'47""N 107°02'29""E), K.D. Hill 5020, L.K. Phan & N.V. Dzu, 10 Mar 1999 (holo HN, iso NSW, K, NY)."


Etymology: Greek tropos a boat keel and phyllon leaf, from the distinctively keeled leaves that are unique in north Vietnam.

Historical notes: Although abundant in the Ha Long Bay World Heritage area, this distinctive taxon has been totally overlooked.

Distinguishing features: Closely allied to C. sexseminifera, but immediately distinguished by the keeled leaves. It also differs in the generally larger proportions in all respects, the broader adult and juvenile leaflets and the larger and broader megasporophyll lamina with a distinct, broad apical spine. It is distinguished from C. ferruginea by the keeled leaves and short, broad, flat leaflets.

Distribution and habitat: A restricted species endemic in Vietnam, known from Cat Ba and other islands in Haiphong Harbour, and on similar limestone bluffs on the adjacent mainland. This species shows the same habitat preference as C. sexseminifera and C. ferruginea, growing on bare limestone faces on steep limestone bluffs, with no soil accumulation at the roots.

Conservation status: Not considered to be at risk. IUCN (1994) Red List status LR nt.
Photo Ken Hill
Photo Ken Hill

Description:

Stems arborescent or acaulescent, to 0-1 m tall, 8-15 cm diam. at narrowest point; 10-30 leaves in crown.

Leaves deep green or grey-green, semiglossy, 70-120 cm long, strongly keeled or moderately keeled (opposing leaflets inserted at 90-120° on rachis), with 100-170 leaflets, with brown tomentum shedding as leaf expands; rachis consistently terminated by paired leaflets. Petiole 10-35 cm long (15-30% of total leaf), petiole glabrous, unarmed or spinescent for 5-80% of length. Basal leaflets not gradually reducing to spines, 50-80 mm long.

Median leaflets simple, strongly discolorous, 120-180 mm long, 7-12 mm wide, inserted at 40-70° to rachis, decurrent for 2-6 mm, narrowed to 2.5-3.5 mm at base (to 20-35% of maximum width), 10-16 mm apart on rachis; median leaflets section flat; margins flat, or slightly recurved; apex aristate, spinescent; midrib raised above, raised below.

Cataphylls narrowly triangular, soft, pilose, 30-50 mm long, persistent.

Pollen cones narrowly ovoid to fusiform, orange, 15-30 cm long, 5-8 cm diam.; microsporophyll lamina soft, not dorsiventrally thickened, 20-30 mm long, 11-15 mm wide, fertile zone 10-28 mm long, sterile apex 2-4 mm long, raised, apical spine rudimentary or absent, sharply upturned, 0-3 mm long.

Megasporophylls 8-12 cm long, brown-tomentose; ovules 2-6, glabrous; lamina orbicular, 90-120 mm long, 60-65 mm wide, deeply pectinate, with 24-34 soft lateral spines 25-35 mm long, 2-3 mm wide, apical spine distinct from lateral spines, 40-45 mm long, 4-6 mm wide at base.

Seeds ovoid, 20-28 mm long, 18-25 mm wide; sarcotesta yellow, not pruinose, 1-2 mm thick; fibrous layer absent; sclerotesta smooth to verrucose. Spongy endocarp absent.


The Cycad Pages

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Written and maintained by Ken Hill 1998-2010
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