''Cycas inermis'' de Loureiro J (1793) "Fl. Cochinch., ed. 2'', 2: 776-77. is a

vascular plant Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They ...

belonging to the family

Cycadaceae ''Cycas'' is a genus of plants belonging to a very ancient lineage, the Cycadophyta, which are not closely related to palms, ferns, trees or any other modern group of plants. They are evergreen perennials which achieved their maximum diversity in ...

, endemic to central and southern

Vietnam Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making it ...

.''Cycas inermis''
, in The Cycad Pages (retrieved 17 February 2020). Its name in Vietnamese is ''Thiên tuế'' or ''Tuế lá quyết''.

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. 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

leaf A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...

lets, 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 Dioecy (; ; adj. dioecious , ) is a characteristic of a species, meaning that it has distinct individual organisms (unisexual) that produce male or female gametes, either directly (in animals) or indirectly (in seed plants). Dioecious reproducti ...

species with male specimens that have

microspore Microspores are land plant spores that develop into male gametophytes, whereas megaspores develop into female gametophytes. The male gametophyte gives rise to sperm cells, which are used for fertilization of an egg cell to form a zygote. Megaspor ...

s dispersed from cones of ovoid shaped terminals, 120 mm long and 80 mm wide. Female specimens bear

megaspore Megaspores, also called macrospores, are a type of spore that is present in heterosporous plants. These plants have two spore types, megaspores and microspores. Generally speaking, the megaspore, or large spore, germinates into a female gametoph ...

s 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 A sporophyll is a leaf that bears sporangia. Both microphylls and megaphylls can be sporophylls. In heterosporous plants, sporophylls (whether they are microphylls or megaphylls) bear either megasporangia and thus are called megasporophylls, or mi ...

is a defining feature, with laminae which de Louriero described as "laciniate" (fringed with lateral narrow pointed lobes).

Distribution and habitat

It is widespread in coastal areas of southern and central Vietnam and fairly common where semi-deciduous and evergreen

seasonal tropical forest Seasonal tropical forest, also known as moist deciduous, semi-evergreen seasonal, tropical mixed or monsoon forests, typically contain a range of tree species: only some of which drop some or all of their leaves during the dry season. This tropi ...

s survive. It thrives on granitic, volcanic-metamorphic or volcanic-basaltic

soils Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former term ...

. It is found from near

Da Nang Nang or DanangSee also Danang Dragons ( ; vi, Đà Nẵng, ) is a class-1 municipality and the fifth-largest city in Vietnam by municipal population. It lies on the coast of the East Sea of Vietnam at the mouth of the Hàn River, and is o ...

to Khanh Hoa Province and south to

Cát Tiên National Park Cát Tiên National Park ( vi, Vườn quốc gia Cát Tiên) is a national park located in the south of Vietnam, belonging to the area of 3 provinces Đồng Nai, Bình Phước and Lâm Đồng. It is approximately 150 km north of ...

Conservation status

The IUCN Red List classifies ''C. inermis'' as a vulnerable species.

References

Whitelock, Loran M., The Cycads, Timber Press, 2002, . Haynes J.L, World List of Cycads: A Historical Review (PDF), IUCN / SSC Cycad Specialist Group, 2012. * * {{Taxonbar, from=Q10262626 inermis Endemic flora of Vietnam Vulnerable flora of Asia Plants described in 1793