Cycas inermis

Cycas inermis [1] is a vascular plant belonging to the family Cycadaceae, endemic to central and southern Vietnam.[2] Its name in Vietnamese is Thiên tuế or Tuế lá quyết.

Cycas inermis
C. inermis male in Cat Tien National Park
C. inermis with megaspores Roy Bateman, taken Oct 2015
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Division: Cycadophyta
Class: Cycadopsida
Order: Cycadales
Family: Cycadaceae
Genus: Cycas
Species:
C. inermis
Binomial name
Cycas inermis
Lour., 1793
Synonyms

Cycas revoluta var. inermis (Lour.) Miq.
Cycas siamensis subsp. inermis (Lour.) J.Schust.

Description

The name Cycas inermis, meaning "unarmed", may be confusing because spines, albeit very small ones, are present on the petiole. The trunk of this cycad is erect with growth rings (see illustration): it is up to 1.5–4 m high and with a diameter of 80–140 mm.[2]

The fronds are pinnate, 2.2–3 m, surrounding the crown at the apex of the stem, with a long petiole 650–800 mm; each rachis is composed of 130-230 pairs of lanceolate leaflets, with an entire and toothed margin, on average, 290–350 mm long, dark green, placed on the spine at an angle of 60-80°.

It is a dioecious species with male specimens that have microspores dispersed from cones of ovoid shaped terminals, 120 mm long and 80 mm wide. Female specimens bear megaspores that are found in large numbers in the upper part of the stem, with the appearance of pinnate leaves that enclose the ovules, in clumps of 4. The seeds are oblong, 50–60 mm long, coated with an orange-brown tegument when ripe. The megasporophyll is a defining feature, with laminae which de Louriero described as "laciniate" (fringed with lateral narrow pointed lobes).[2]

Distribution and habitat

It is widespread in coastal areas of southern and central Vietnam and fairly common where semi-deciduous and evergreen seasonal tropical forests survive. It thrives on granitic, volcanic-metamorphic or volcanic-basaltic soils. It is found from near Da Nang to Khanh Hoa Province and south to Cát Tiên National Park.

Conservation status

The IUCN Red List classifies C. inermis as a vulnerable species.[3]

References
  1. de Loureiro J (1793) "Fl. Cochinch., ed. 2, 2: 776-77.
  2. Cycas inermis, in The Cycad Pages (retrieved 17 February 2020).
  3. Nguyen, H.T., Cycas inermis, on the IUCN Red List of Threatened Species, version 2016.3, IUCN, 2016.

Whitelock, Loran M., The Cycads, Timber Press, 2002, ISBN 0-88192-522-5. Haynes J.L, World List of Cycads: A Historical Review (PDF), IUCN / SSC Cycad Specialist Group, 2012.

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