''Microcycas'' is a genus of

cycad Cycads are seed plants that typically have a stout and woody (ligneous) trunk with a crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants of a species are either male o ...

s in the family

Zamiaceae The Zamiaceae are a family of cycads that are superficially palm or fern-like. They are divided into two subfamilies with eight genera and about 150 species in the tropical and subtropical regions of Africa, Australia and North and South Americ ...

containing only one species, ''Microcycas calocoma'', endemic to a small area in western

Cuba Cuba ( , ), officially the Republic of Cuba ( es, República de Cuba, links=no ), is an island country comprising the island of Cuba, as well as Isla de la Juventud and several minor archipelagos. Cuba is located where the northern Caribb ...

Pinar del Río Province Pinar del Río is one of the provinces of Cuba. It is at the western end of the island of Cuba. Geography The Pinar del Río province is Cuba's westernmost province and contains one of Cuba's three main mountain ranges, the Cordillera de Guanig ...

Description

The plant grows up to 10 m tall with an upright, sometimes branching trunk that grows to 30–60 cm in diameter. The

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

are dark green and 0.6–1.2 m long. One unique character is that the leaves appear to be truncated near the apex because the middle and distal leaflets have similar lengths. The petioles are 8–10 cm long and lack spines; the

rachis In biology, a rachis (from the grc, ῥάχις [], "backbone, spine") is a main axis or "shaft". In zoology and microbiology In vertebrates, ''rachis'' can refer to the series of articulated vertebrae, which encase the spinal cord. In this c ...

es also lack spines. leaflets are light to dark green, lanceolate, articulate at the base, and leathery with an entire margin. Middle leaflets are 15–25 cm long by 0.8–1 cm wide. Male cones are cylindrical, 25–30 cm long and 5–8 cm in diameter, yellow-brown, and hairy. Seed cones are broadly cylindrical, 50–90 cm long and 13–16 cm in diameter, yellow-brown, and hairy. The

sporophyll 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 ...

s have two round apical projections. The elliptical

seed A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiosper ...

s are pink or red in color, 3.5–4 cm long and 2–2.5 cm in diameter. File:Microcycas calocoma 0zz.jpg, Plant File:Microcycas calocoma 3zz.jpg, Leaves File:Microcycas calocoma 4zz.jpg, Trunk File:Microcycas MaleDehiscentCone.jpg, Cone File:Microcycas calocoma 5zz.jpg, Trunk

Distribution

In its native range, ''Microcycas calocoma'' grows in small groups of 10–50 plants in montane forests at 85–250 m elevation. It also grows on the slopes of gullies and in open grassland and scrub at 50 m altitude. Soil types range from alkaline loam developed on

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms w ...

to acidic clays containing

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...

. In many of these groups of plants, however, the

sex ratio The sex ratio (or gender ratio) is usually defined as the ratio of males to females in a population. As explained by Fisher's principle, for evolutionary reasons this is typically about 1:1 in species which reproduce sexually. Many species dev ...

is very unbalanced, resulting in a low output of seedlings. Humans have negatively impacted the species through forestry operations, clearing of land, and pesticide use. Because of the plant's graceful and ornamental appearance, harvesting of plants and seeds by growers has also seriously affected ''M. calocoma''. Many populations are now protected in reserves.

Conservation

The species is critically endangered, with a world population of only about 600 plants. It is listed under

CITES Appendix I CITES (shorter name for the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention) is a multilateral treaty to protect endangered plants and animals from the threats of intern ...

which prohibits international trade in specimens of this species except when the purpose of the import is not commercial, for instance for scientific research. Although ''Microcycas calocoma''s round crown and shiny drooping leaves make it a very ornamental plant, cultivation is limited due to the lack of growing material. Locals have used the plant's toxic roots as a rat poison.

References

*Jones, David L. ''Cycads of the World: Ancient Plants in Today's Landscape''. Washington, D.C.: Smithsonian Institution Press, 2002. .
''Microcycas calocoma'' in The Cycad Pages
{{Taxonbar, from=Q1057029 Zamiaceae Endemic flora of Cuba Trees of Cuba Monotypic gymnosperm genera Critically endangered flora of North America Plants described in 1868