Photo Ken Hill
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The Cycad Pages
Cycas petraea

Cycas petraea A. Lindstr. & K.D. Hill, Brittonia 54 (4): 299. fig. 1 (dated 2002) (2003). H—BKF
"TYPE: Thailand, Loei, Phu Kradung, Ban Pong Khao, K.D. Hill 5086 & Poonsak Vatcharakorn, 1 Feb 2000 (holo BKF, iso K, NSW, NY)."[NSW]


Etymology: From the Latin petraeus, of rocky places, referring to the habitat on bare limestone cliffs and boulders.

Distinguishing features: This species most resembles C. clivicola in the smooth trunk with a swollen base, the flat, glossy bright green leaflets and the precipitous limestone habitat. It differs in the overall larger stature with larger leaves and leaflets, and most clearly in the much larger male cones with longer microsporophylls and longer apical spines on the microsporophylls.

Distribution and habitat: Locally abundant in open scrub with Dracaena, Euphorbia, bamboos and numerous climbers on steep to precipitous limestone outcrops with no soil cover. Known only from a single line of limestone mountains flanking the Phu Kra Dung massif to the east.

Conservation status: although localised, this is an abundant species, mostly occurring in relatively inaccessable sites. The present range and population size is substantially untouched, and there is little threat to the survival of the species. The appropriate IUCN Red List category would be LR nt (IUCN, 1994).
Photo Ken Hill
Photo Ken Hill

Description:

Stems arborescent, to 6 m tall, 15-20 cm diam. at narrowest point; 50-100 leaves in crown.

Leaves bright green, highly glossy, 140-230 cm long, flat (not keeled) in section (opposing leaflets inserted at 180° on rachis), with 140-230 leaflets, with white or orange tomentum shedding as leaf expands; rachis usually terminated by paired leaflets. Petiole 25-40 cm long (15-20% of total leaf), petiole glabrous, unarmed or spinescent for 0-50% of length. Basal leaflets not gradually reducing to spines, 100-120 mm long.

Median leaflets simple, strongly discolorous, 230-290 mm long, 10-13 mm wide, inserted at 50-70° to rachis, decurrent for 3-6 mm, narrowed to 2-3 mm at base (to 15-30% of maximum width), 13-17 mm apart on rachis; median leaflets section flat; margins flat; apex acute, not spinescent; midrib raised above, raised below.

Pollen cones ovoid or narrowly ovoid, orange or brown, 30-40 cm long, 14-18 cm diam.; microsporophyll lamina firm, not dorsiventrally thickened, 40-50 mm long, 14-18 mm wide, fertile zone 32-40 mm long, sterile apex 5-7 mm long, level, apical spine prominent, sharply upturned or gradually raised, 12-20 mm long.

Megasporophylls 18-22 cm long, grey-tomentose or brown-tomentose; ovules 2-6, glabrous; lamina orbicular or ovate, 100-170 mm long, 45-90 mm wide, deeply pectinate, with 20-28 soft lateral spines 20-40 mm long, 3-4 mm wide, apical spine distinct from lateral spines, 55-85 mm long, 6-9 mm wide at base.

Seeds flattened-ovoid; sarcotesta yellow, not pruinose; 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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