''Asplenium arcanum'' is a fern known from western

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

and

Nicaragua Nicaragua, officially the Republic of Nicaragua, is the geographically largest Sovereign state, country in Central America, comprising . With a population of 7,142,529 as of 2024, it is the third-most populous country in Central America aft ...

Description

Roots and stipes

''Asplenium arcanum'' has fibrous roots and an upright

rhizome In botany and dendrology, a rhizome ( ) is a modified subterranean plant stem that sends out roots and Shoot (botany), shoots from its Node (botany), nodes. Rhizomes are also called creeping rootstalks or just rootstalks. Rhizomes develop from ...

(underground stem). The rhizome bears narrow, blackish scales, long and wide, which are

clathrate A clathrate is a chemical substance consisting of a lattice (group), lattice that traps or contains molecules. The word ''clathrate'' is derived from the Latin language, Latin (), meaning 'with bars, Crystal structure, latticed'. Most clathrate ...

(bear a lattice-like pattern) and have untoothed margins. The fronds grow in clumps and are, including the stipe (the stalk of the leaf, below the blade), long. The stipes are dark purple in color at the base, becoming green towards the blade, lack

wing A wing is a type of fin that produces both Lift (force), lift and drag while moving through air. Wings are defined by two shape characteristics, an airfoil section and a planform (aeronautics), planform. Wing efficiency is expressed as lift-to-d ...

s, and have no hairs or scales except at the very base. They range from long and wide, and typically make up one-half to two-thirds of the total length of the frond.

Leaves

Each leaf bears from one to five pairs of pinnae (the first subdivisions of the leaf). The pair closest to the base is the largest. The

rachis In biology, a rachis (from the [], "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 case the ''rachi ...

(leaf axis) is green beneath, sometimes with streaks of purple at the base, smooth, and has small wings on the upper side, from wide.

Sori and spores

Fertile fronds bear from one to three pairs of sori per pinnule on both sides of the costule (pinnule midvein). They are covered by indusia long and wide, with jagged margins. The spores are kidney-shaped.

Similar species

Specimens have in the past been identified as, or thought to be similar to, '' A. fragrans'', '' A. minimum'', '' A. pumilum'', and '' A. tenerrimum''. It differs from ''A. fragrans'' by the dark purple (rather than green) color at the base of its stipe, from ''A. pumilum'' by the lack of long whitish hairs both above and below the leaf, from ''A. tenerrimum'' by the enlargement of the side of the lowest pinna towards the leaf base, and from ''A. minimum'' by the deeply cut and toothed pinnae and pinnules (rather than rounded and lobed).

Taxonomy

Material of this species was described by George E. Davenport in 1894 as a deeply cut variety of ''A. pumilum'', var. ''laciniatum'', based on material collected in

Jalisco Jalisco, officially the Free and Sovereign State of Jalisco, is one of the 31 states which, along with Mexico City, comprise the 32 Political divisions of Mexico, Federal Entities of Mexico. It is located in western Mexico and is bordered by s ...

Cyrus Pringle Cyrus Guernsey Pringle (May 6, 1838 – May 25, 1911) was an American botanist who spent a career of 35 years cataloguing the plants of North America. He was a prolific collector and accomplished botanical explorer. Early life He was born on May ...

. It was described as a species by Alan R. Smith in 2004 based on a specimen collected near

San Blas, Nayarit San Blas is both a municipality and municipal seat located on the Pacific coast of Mexico in Nayarit. City San Blas is a port and popular tourist destination, located about north of Puerto Vallarta, and west of the state capital Tepic, and thr ...

Roxana Stinchfield Ferris Roxana Judkins Stinchfield Ferris (April 13, 1895 – June 30, 1978) was an American botanist. She was born in Sycamore, California, to Moses and Annie Stinchfield. She was named after her grandmother, Roxany Judkins. In 1916, Stinchfield Ferri ...

. He gave it the epithet ''arcanum'' in reference to the unclear and mysterious relationship between this species and other spleenworts; it is roughly intermediate in form between ''A. tenerrimum'' and ''A. pumilum'', but has well-formed spores, so it is not a first-generation hybrid.

Distribution and habitat

''Asplenium arcanum'' grows on stream banks and on wooded hillsides in the states of

Nayarit Nayarit, officially the Free and Sovereign State of Nayarit, is one of the 31 states that, along with Mexico City, comprise the Political divisions of Mexico, Federal Entities of Mexico. It is divided in Municipalities of Nayarit, 20 municipalit ...

and

Sinaloa Sinaloa (), officially the (), is one of the 31 states which, along with Mexico City, compose the Federal Entities of Mexico. It is divided into 18 municipalities, and its capital city is Culiacán Rosales. It is located in northwest Mexic ...

, at altitudes from . It has also been collected once from dry forest in Nicaragua, at an altitude between .

Notes and references

References

Works cited

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External links

Holotype
from JSTOR Global Plants. {{Taxonbar, from=Q15609551 arcanum Ferns of Mexico Flora of Nicaragua