Cycas nongnoochiae K. D. Hill (1999)
Hill.,K.D. 1999. The genus Cycas (Cycadaceaea) in Thailand. Brittonia 51(1):48-73.

Plant arborescent stem erect, usually unbranched, to 2, sometimes 5 m tall, 10-18 cm diam. At narrowest point, bark thick, hard, corky, with regular polygonal fracturing dark grey. Leaves numerous, grey-green to bluish, semiglossy, 0.8-1.35 m long, flat (not keeled) in section, with 120-200 pinnae, opposing pinnae inserted at 180? on rachis consistently terminated by a spine 4-21 mm long. Petiole 23-35 cm long (20-30% of total leaf), glabrous, spinescent for 10-50% of length. Basal pinnae gradually reducing to spines, pinnae 2-8 cm long. Median pinnae simple, glabrous, strongly discolorous, inserted at 65-75? to rachis, 12-18 cm x 7-8.5 mm, section flat, margins flat to slightly recurved, decurrent for 4-7 mm, narrowed to 3-4 mm at base, (to 40-50% of maximum width), 8-11 mm apart on rachis; apex acute, spinescent; midrib flat above, raised below. Tomentum white, loose and shed early. Cataphylls soft, 4-7 cm long, orange-brown to brown-tomentose. Microsporangiate cones narrowly ovoid, pale yellow or green, 15-22 cm long, 7-9 cm diam. Microsporophyll lamina 22-30 x 14-19 mm, fertile zone 15-25 mm long, sterile zone 5-7 mm long, level, apical spine prominent, sharply upturned, 7-9 mm long. Megasporophylls 16-19 cm long, white to yellow-tomentose; ovules 2-4 glabrous; lamina orbicular to ovate, 85-100 x 60-70 mm. deeply pectinate, with 36-52 soft lateral spines 20-24 x 2 mm; apical spine distinct from lateral spines, 15-25 mm long, 4 mm wide at base. Seeds flattened-ovoid, 35 x 28-35 mm, sarcotesta yellow, not or slightly pruinose, 2 mm thick; fibrous layer present (weakly developed); sclerotesta smooth; spongy layer absent.

Distinguishing features.-The combination of tall arborescent stems and dark, deeply fissured bark distinguish this species. Cycas nongnoochiae has bark and tomentum similar to C. siamensis, but habit and male and female sporophylls more greatly resemble those of C. clivicola. Leaves are more or less intermediate between the two, and C. nongnoochiae may have originated as a hybrid. It is clearly now stabilized and reproducing, and is best regarded as a separate species.
Distribution and habitat.-Known at present only from limestone outcrops near Tak Fa, 15?21'N, 100?28'E (Fig.3). This species is locally abundant, in full sun in low scrub on steep limestone bluffs, often growing in crevices in bare limestone.

Conservation status.-Apparently quite restricted in occurrence and under some pressure from plant collectors, this species should be regarded as threatened. The appropriate IUCN Red List category would be ‘Lower Risk-near threatened’ (IUCN, 1994).

Etymology.-The specific epithet commemorates the Nong Nooch Tropical Garden. The feminine termination is international, in reference to the founder of the garden, after whom the garden was named