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Froelichia alata

Interesting Facts

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Description

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Family Amaranthaceae

Herbs, clambering subshrubs , shrubs , or lianas. Leaves alternate or opposite, entire, exstipulate . Flowers small, bisexual or unisexual , or sterile and reduced, subtended by 1 membranous bract and 2 bracteoles, solitary or aggregated in cymes. Inflorescences elongated or condensed spikes (heads ), racemes , or thyrsoid structures of varying complexity. Bracteoles membranous or scarious . Tepals 3-5, membranous, scarious or subleathery, 1-, 3-, 5-, or 7(-23) -veined. Stamens as many as tepals and opposite these, rarely fewer than tepals; filaments free , united into a cup at base or ± entirely into a tube , filament lobes present or absent, pseudostaminodes present or absent; anthers (1- or) 2-loculed, dorsifixed , introrsely dehiscent . Ovary superior, 1-loculed; ovules 1 to many; style persistent , short and indistinct or long and slender; stigma capitate, penicillate , 2-lobed or forming 2 filiform branches. Fruit a dry utricle or a fleshy capsule, indehiscent, irregularly bursting, or circumscissile. Seeds lenticular , reniform , subglobose, or shortly cylindric , smooth or verruculose .

About 70 genera and 900 species: worldwide; 15 genera (one introduced ) and 44 species (three endemic, 14 introduced) in China.

Morphology of the androecium, perianth (tepals), and the inflorescence has traditionally been used to circumscribe genera and tribes . Pseudostaminodia are interstaminal appendages with variously shaped apices. Filament appendages are the lateral appendages of filaments (one on each side) . The basic structure of the inflorescence is the cyme (branchlets arising from the bracteole axils, the bracteoles serving as bracts for upper flowers), which can be reduced to one flower with two bracteoles and a bract. Units of dispersal vary considerably (capsules opening with lower part persistent, flower and bracteoles falling together, or cymose partial inflorescences breaking off above bract) and can be characteristic for genera. Several genera possess long trichomes serving dispersal at the base of the tepals.[1]

Genus Froelichia

Herbs [shrubs ], annual or perennial . Stems erect or procumbent , simple to much-branched, sometimes broomlike, usually richly pubescent . Leaves opposite, sessile or short-petiolate, most abundant on proximal 1/2 of plant; blade linear , lanceolate, oblanceolate , oblong , or orbiculate, fulvous abaxially, margins entire, usually pubescent. Inflorescences terminal , erect, pedunculate , spiciform , mostly compound , usually elongate and interrupted , or rounded and headlike; rachis consisting of spirally arranged bracts that adaxially subtend 2 concave imbricate bracteoles enclosing and falling with the flowers, silky or woolly . Flowers bisexual ; tepals 5, connate at least to middle into tube ; lobes lanceolate to acute; tube 2-lipped, 5-lobed, surpassing bracteoles, lanate , becoming indurate in fruit and developing lateral wings or crests and, in some species, facial tubercles or spines; stamens 5; filaments connate into cylindric to flask-shaped, 5-lobed tube, lobes (pseudostaminodes) with margins entire or shallowly notched , apex blunt to acute; anthers attached at sinuses, 2-locular; ovule 1; style 1, short or elongate, shorter than staminal tube; stigmas sessile, minutely 2-fid to capitate or penicillate . Utricles enclosed by indurate perianth tube, ovoid or flask-shaped, membranaceous , indehiscent. Seeds 1, obovoid or lenticular , germinating while enclosed by perianth tube. x = 8.

Species ca. 16: temperate and tropical regions of the Western Hemisphere.

Froelichia is most abundant in the Sonoran and Chihuahuan deserts, the plains of southern Texas and Florida in North America, and the grasslands of South America, particularly eastern Paraguay and southern Brazil. Two species (F. lanigera Andersson, F. nudicaulis Hooker f.) are endemic to the Galapagos Islands.

Froelichia is divided into sect. Hoplotheca (Nuttall) Moquin-Tandon, with stigmas interpreted as being capitate (the capitate form is derived from a bifid structure), and sect. Dilopha Moquin-Tandon, with penicillate stigmas. Section Dilopha is restricted to South America; sect. Hoplotheca to North America and South America.

Evolutionarily there are two principle clades occuring across North America. One clade comprises the perennial Froelichia interrupta comprised of three varieties occuring south through most of Mexico to Nicaragua. Morphologically the group is distinguished by plants with relatively sparsely flowered inflorescences with the flowers arranged in a 3-ranked spriral. The pseudostaminodes are short and exhibit a blunt apex. The second clade occurs to the north and comprises a mix of annual and perennial species, including the taxa described here and F. "xantusii" R. A. McCauley, which is endemic to southern Baja California.

Froelichia is probably best known as a roadside weed because it thrives in occasionally disturbed environments with little competition . It is also a common member of coastal pine areas, particularly along the Gulf Coast. The plants are pioneers in disturbed sandy soils, can become agricultural pests in rare instances, and form large patches in fallow fields or pastures. Introduction of Froelichia has occurred throughout much of the United States (F. gracilis) ; F. floridana is naturalized in Queensland, Australia, most likely from contaminated seed in the mid-1950s.

Confusion in the identity of Froelichia species has been due in large part to the over-reliance on variable characters, principally the nature of the lateral wings on the mature perianth. Recent revisionary work (R. A. McCauley 2002) has served to identify more stable characters for identification and has led to recircumscriptions of the geographic ranges of the species.[2]

Taxonomy

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Notes

Publishing author : S.Watson Publication : Proc. Amer. Acad. Arts xxi. (1886) 437.

Similar Species

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Members of the genus Froelichia

ZipcodeZoo has pages for 8 species, subspecies, varieties, forms, and cultivars in this genus:

F. arizonica (Arizona Snake-Cotton) · F. drummondii (Drummond's Snake-Cotton) · F. floridana (Cottonweed) · F. floridana var. campestris (Plains Snakecotton) · F. floridana var. floridana (Plains Snakecotton) · F. gracilis (Slender Cottonweed) · F. interrupta (Texas Snake-Cotton) · F. latifolia (Broadleaf Snake Cotton)

More Info

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Further Reading

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Notes

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Contributors

Identifiers

Footnotes

  1. Bojian Bao, Thomas Borsch & Steven E. Clemants "Amaranthaceae". in Flora of China Vol. 5 Page 415. Published by Science Press (Beijing) and Missouri Botanical Garden Press. Online at EFloras.org. [back]
  2. Ross A. McCauley "Froelichia". in Flora of North America Vol. 4 Page 406, 443, 444. Oxford University Press. Online at EFloras.org. [back]
Last Revised: 2012-07-20