Photo Ken Hill
The Cycad Pages
Cycas inermis

Cycas inermis Lour., "Fl. Cochinch., ed. 2, 2: 776-777" (1793).
"TYPE: Vietnam, Saigon, 1787, Loureiro 3 (holo BM)."

Typification: The type specimen is of a leaf apex only, but closely matches the forest species e.g. from Cat Tien National Park. Louriero's description states that the megasporophyll is "laciniate", but no plant matching both the type (leaf) specimen and this megasporophyll description has been collected in Vietnam. It is possible that the description was a composite based on disparate specimens. For this study, the name "inermis" is applied to the inland forest species from south and central Vietnam that matches the type specimen. It is possible although unlikely that future discoveries may require a change to this nomenclatural application. Although named for the unarmed petiole, petiole spinescence varies, and wholly unarmed individuals are uncommon. Etymology: From the Latin inermis, unarmed, reference uncertain, since the petiole is not thornless in this species. The soft leaves in contrast to the stiff pungent leaflets of C. revoluta may have suggested the name.

Literature: Oudemans 1868, Gaudichaud 1829, Leandri 1931

Illustrations: Warburg 1900.

Historical notes: Portugese colonial explorer Joao de Loureiro described C. inermis in 1790 on the basis of plants he observed and collected in the French territory of Cochinchina. Although the third species of Cycas to be recognised, this taxon has never been properly understood. Gaudichaud (1829) enumerated it in his discussion of the genus, based entirely on de Loureiro. Miquel (1842) was next to mention the name, expressing an opinion that it may be the same as C. revoluta var. planifolia. Miquel later (1851) figured in detail as C. inermis specimens that were clearly closely allied to C. revoluta, and bore very little resemblance to de Loureiro's type. De Candolle (1868) drew his description from Miquel, and subsequent authors followed (Regel 1876, Thiselton-Dyer 1902 [?and Oudemans]). Warburg (1900) maintained it as separate, and Tandy (1927) pointed out Miquel's error. Metcalf (1942) applied the name C. inermis to C. sexseminifera, and Leandri (1931) applied it to material from southern Vietnam. Later treatments from China (Cheng et al. 1975, Zhou et al. 1990) also confused it with C. sexseminifera. More recently, the treatment of the cycads for the Flore du Cambodge Laos et Vietnam (Hiep & Vidal 1996) has this species confused with the taxon now known as C. condaoensis.

Distinguishing features: Readily distinguished within Vietnam by the narrow megasporophyll lamina with short lateral teeth and the seeds with a fibrous layer in the sarcotesta. This species is nearest to C. macrocarpa from Thailand and Malaysia, differing in the shorter lateral spines on the megasporophyll.

Distribution and habitat: Widely distributed on the near-coastal ranges in central and southern Vietnam, from near Da Nang south to Nam Cat Tien National Park. Locally common in closed evergreen or semideciduous forests on flat or elevated sites on granite, metamorphic or basaltic volcanic substrates. C. inermis often grows on steep slopes or local slight stony rises where the drainage would be greater.

Conservation status: Not considered to be at risk, although further study of distribution is required. IUCN (1994) Red List status DD/VU?.
Photo Ken Hill
Photo Ken Hill


Stems arborescent, to 1.5-4 m tall, 8-14 cm diam. at narrowest point; 6-35 leaves in crown.

Leaves deep green, highly glossy, 220-300 cm long, flat (not keeled) in section (opposing leaflets inserted at 180° on rachis), with 130-230 leaflets, with white tomentum shedding as leaf expands; rachis consistently terminated by paired leaflets. Petiole 65-80 cm long (25-35% of total leaf), petiole glabrous, spinescent for 70-100% of length. Basal leaflets not gradually reducing to spines.

Median leaflets simple, strongly discolorous, 290-350 mm long, 14-18 mm wide, inserted at 60-80° to rachis, decurrent for 5-7 mm, narrowed to 3-4.5 mm at base (to 20-30% of maximum width), 18-22 mm apart on rachis; median leaflets section flat; margins flat to slightly recurved; apex softly acuminate, not spinescent; midrib raised above, flat below.

Cataphylls linear, pungent, pilose, 40-50 mm long, articulated.

Pollen cones ovoid, cream, 12 cm long, 8 cm diam.; microsporophyll lamina firm, not dorsiventrally thickened, apical spine prominent, sharply upturned, 10 mm long.

Megasporophylls 20 cm long, grey-tomentose; ovules 4, glabrous; lamina ovate to lanceolate, 50-70 mm long, 30-70 mm wide, regularly dentate, with 18-26 pungent lateral spines 4-5 mm long, 1-1.5 mm wide, apical spine distinct from lateral spines, 20-25 mm long, 3 mm wide at base.

Seeds oblong, 50-60 mm long, 38-50 mm wide; sarcotesta orange, slightly pruinose, 5 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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