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The Cycad Pages
Cycas riuminiana

Cycas riuminiana Porte ex Regel, Gartenflora 12: 16-17 (1863).
"TYPE: Regel 6210, lecto K, fide de Laub. & Adema (doubtful) or ex horto Bot. Petropolitano, leg. ign. 70.7 (neotype (fide Stevenson & Hill) LE)."


Lectotype (K)
Etymology: Honouring - Riumin, president of the Moscow Horticultural Society.

Historical notes: Described in 1863 by German-born botanist Eduard Auguste von Regel (1815-1892), Scientific Director and later Director of the Imperial Botanic Garden in St Petersburg, 1855-1892. No type was cited. Plants were imported from Manila by -- Porte and sold by the Moscow Horticultural Society through the Belgian horticultural trading firm of Verschaffelt.

This species was later described as Cycas chamberlainii in 1925 by William H. Brown, Director of the Philippine Bureau of Science, and Raymond Keinholz, Professor of Botany at the University of the Philippines, who also collected the type specimens. The authors noted that `it has been known for some time that ... there was a slender mountain form with small seeds which was possibly, or probably, a distinct species'. Merrill (1923) had also noted small-fruited specimens from Mindoro, Batangas and the Mt Mariveles district of Luzon. Neither Merrill nor Brown and Keinholz were aware of the identity of C. riuminiana and consequently of the priority of this name.

The original holotype or syntype material of C. chamberlainii (in PNH) was destroyed in WW2, but duplicates were widely distributed. No lectotype is chosen because much of the male and female material has been mixed, and clear distinction of material originally coming from individual plants is uncertain.

C. chamberlainii had generally been accepted as a distinct species (Amoroso 1986, Zamora & Co 1986), although Schuster (1932) placed it under C. circinalis subsp. riuminiana var. curranii forma chamberlainii. De Laubenfels and Adema (1998) first recognised the real identity of C. riuminiana, although with an overly wide circumscription and incorrect typification.

Distinguishing features: Readily distinguished in the Philippines by open seed cone with long sporophylls and small seeds with a thin spongy endocarp layer. The similar C. falcata from Sulawesi is distinguished by longer leaves and shorter, softer cataphylls. C. riuminiana also has straight, flat leaflets with flat or slightly recureved margins and the midrib strongly raised above.

Distribution and habitat: Widespread in inland and montain closed forests in the northern parts of the Philippines.

Conservation status: Altough much of such forest area has been cleared or disturbed, large populations of C. riuminiana remain in protected areas such as on Mt Arayat and Mt Dipalayag. Not regarded as threatened. IUCN (1994) Red List status LR cd.
Photo Ken Hill
Photo Ken Hill

Description:

Stems arborescent.

Leaves bright green, highly glossy or semiglossy, 110-180 cm long, with 160-230 leaflets, with white tomentum shedding as leaf expands; rachis usually terminated by a spine 5-10 mm long. Petiole 35-45 cm long (20-25% of total leaf), petiole glabrous, spinescent for 20-50% of length. Basal leaflets not gradually reducing to spines, 120-180 mm long.

Median leaflets simple, weakly discolorous, 240-310 mm long, 8-12 mm wide, inserted at 15-25° to rachis, narrowed to 2-3 mm at base, 10-15 mm apart on rachis; median leaflets section flat; margins slightly recurved; apex aristate, not spinescent; midrib raised above, raised below.

Cataphylls linear, pungent, pilose, persistent.

Pollen cones fusiform, 44-55 cm long, 8-11 cm diam.; microsporophyll lamina firm, not dorsiventrally thickened, 30-37 mm long, 16-22 mm wide, apical spine prominent, sharply upturned, 4-23 mm long.

Megasporophylls 16-19 cm long, brown-tomentose; ovules 4-6, glabrous; lamina lanceolate, 65-85 mm long, 16-20 mm wide, regularly dentate, with 23 pungent lateral spines 1-5 mm long, apical spine distinct from lateral spines, 26-46 mm long.

Seeds flattened-ovoid, 40-50 mm long, 26-30 mm wide; sarcotesta yellow; fibrous layer absent; sclerotesta smooth. Spongy endocarp absent.


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Written and maintained by Ken Hill 1998-2010
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