Etymology: From the Greek dolichos, long, and phyllon, leaf, referring to the long leaves. Historical notes: Although the most widespread and abundant cycad in northern Vietnam, C. dolichophylla was recognized as a distinct species only in the late 1990's. Distinguishing features: This species has been confused with C. balnasae in the past. The robust though usually short aerial trunk, the larger and more numerous leaves with red-brown tomentum and more numerous leaflets that are short, broad and distinctively rounded at the base, and the larger male cones readily distinguish C. dolichophylla fromC. balansae Megasporophylls are similar to those of C. balansae. C. dolichophylla is also part of the complex of closely related taxa that is distributed through northern Vietnam, Laos, northern Thailand and Yunnan and Guangxi in southern China (Section Stangerioides). Distribution and habitat: Locally frequent in more sheltered sites in deep shade in tall closed evergreen forests. A predominantly Vietnamese species, extending from near the Chinese border in the north to Ben En NP in the south, and west to a very short way into eastern Yunnan province in China. This species occurs on loamy soils over limestone, shale, schist or granite, in closed evergreen forests, although today these are often reduced to scrubby regrowth. A population occurring west of the city of Moc Chau has narrow leaflets with slender bases, short to medium petioles and small seeds, and is interpreted as a zone of intergradation with C. collina, which is abundant in higher country to the west. Plants observed in cultivation around Vo Nhai and Yen Son districts, Thai Nguyen Province, were intermediate in form between C. dolichophylla and C. ferruginea, and have been interpreted as hybrid individuals. In this region, C. ferruginea is abundant on steep exposed limestone faces, and C. dolichophylla is abundant in adjacent closed forests on deep heavy soils. Plants observed in cultivation in villages west of Thai Nguyen and said to have been collected locally were morphologically intermediate between C. dolichophylla and C. multifrondis. Conservation status: There is no immediate threat of extinction, although the severe depletion of populations over past decades indicates that conservation action is appropriate, and this species is regarded as vulnerable, IUCN Red List category VU A2c.
Description:
Stems arborescent, to 1.5 m tall, 18-30 cm diam. at narrowest point; 8-40 leaves in crown. Leaves bright green to deep green, highly glossy, 200-450 cm long, flat (not keeled) in section (opposing leaflets inserted at 180° on rachis), with 150-270 leaflets, with orange tomentum shedding as leaf expands; rachis consistently terminated by paired leaflets. Petiole 40-110 cm long (20-35% of total leaf), petiole glabrous, spinescent for 90-100% of length. Basal leaflets not gradually reducing to spines, 90-240 mm long. Median leaflets simple, strongly discolorous, 190-420 mm long, 14-25 mm wide, inserted at 60-85° to rachis, decurrent for 5-8 mm, narrowed to 3-6 mm at base (distinctively rounded at base) (to 20-35% of maximum width), 16-30 mm apart on rachis; median leaflets section flat; margins undulate; apex softly acuminate, not spinescent; midrib raised above, flat below. Cataphylls narrowly triangular, soft, pilose, 80-120 mm long, articulated. Pollen cones narrowly ovoid or fusiform, yellow, 35-50 cm long, 8-10 cm diam.; microsporophyll lamina soft, not dorsiventrally thickened, 30-36 mm long, 9-13 mm wide, fertile zone 27-34 mm long, sterile apex 2-4 mm long, level, apical spine rudimentary or absent, sharply upturned, 0-3 mm long. Megasporophylls 15-26 cm long, brown-tomentose; ovules 2-4, glabrous; lamina orbicular, 60-120 mm long, 50-100 mm wide, deeply pectinate, with 16-26 soft lateral spines 40-50 mm long, 2-3 mm wide, apical spine not distinct from lateral spines. Seeds ovoid or flattened-ovoid or oblong, 40-64 mm long, 33-36 mm wide; sarcotesta yellow, not pruinose, 2-4 mm thick; fibrous layer absent; sclerotesta verrucose. Spongy endocarp absent.
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