Froelichia gracilis |
Amaranthaceae |
|||||||||||||||||||||||||||||||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
slender cotton-weed, slender Snake-cotton |
amaranth family |
|||||||||||||||||||||||||||||||||||||||||||||||||||||
Habit | Plants annual or short-lived perennial; taproots narrow, enlarged when perennial, semiwoody. | Herbs, rarely subshrubs, annual or perennial; trichomes simple (branched in Tidestromia). | ||||||||||||||||||||||||||||||||||||||||||||||||||||
Stems | several (rarely 1), erect or ascending, sometimes procumbent, usually much-branched from base, slender, 1–5(–10) dm, densely or sparsely villous-tomentose with grayish white hairs. |
without nodal spines (Amaranthus spinosus sometimes with paired nodal spines). |
||||||||||||||||||||||||||||||||||||||||||||||||||||
Leaves | predominant on proximal 1/3 of plant, often basal, sessile; blade linear to lanceolate or lance-elliptic, largest leaves 1.6–9(–13.5) × 0.2–0.9(–1.2) cm, base acuminate or attenuate, apex acute to acuminate, canescent or sericeous adaxially, sericeous-tomentose with white or gray hairs abaxially. |
alternate or opposite, exstipulate, usually petiolate; blade margins entire (entire or serrulate in Iresine; entire, crispate, or erose in Amaranthus). |
||||||||||||||||||||||||||||||||||||||||||||||||||||
Inflorescences | cymules arranged in spikes, panicles, thyrses, heads, glomerules, clusters, or racemes; each flower subtended by 1 bract and 2 bracteoles (latter sometimes 1 or absent in Amaranthus). |
|||||||||||||||||||||||||||||||||||||||||||||||||||||
Spikes | sparsely branched, flowers arranged in 3-ranked spiral; bracteoles stramineous or blackish, glabrous. |
|||||||||||||||||||||||||||||||||||||||||||||||||||||
Flowers | 2.4–3.8 mm; perianth lobes oblong-linear, apex acute or acutish, pubescence grayish; filament lobes stramineous or blackish, blunt. |
bisexual or unisexual (plants then monoecious or dioecious), hypogynous, generally small or minute; tepals mostly (1–)4–5 or absent, distinct or connate into cups or tubes, scarious, chartaceous, membranaceous, or indurate; stamens 2–5, filaments basally connate into cups or tubes, rarely distinct, alternating with pseudostaminodes (appendages on staminal tubes) or not, anthers 2-locular with 1 line of dehiscence or 4-locular with 2 lines of dehiscence; ovary superior, 1-locular; ovules 1 or, rarely, 2–many; style 1 or absent; stigmas 1–3(–5). |
||||||||||||||||||||||||||||||||||||||||||||||||||||
Fruits | utricles, dry, dehiscent or not. |
|||||||||||||||||||||||||||||||||||||||||||||||||||||
Seeds | black, reddish brown, or brown, lenticular, subglobose or globose (rarely cylindric), usually small; embryo peripheral, surrounding mealy perisperm. |
|||||||||||||||||||||||||||||||||||||||||||||||||||||
Utricles | 2.5–5 × 2.7–4 mm, apex slightly oblique, with irregularly and deeply cut (“spiny”) lateral wings, both surfaces of perianth with distinct spines or tubercles. |
|||||||||||||||||||||||||||||||||||||||||||||||||||||
2n | = 54. |
|||||||||||||||||||||||||||||||||||||||||||||||||||||
Froelichia gracilis |
Amaranthaceae |
|||||||||||||||||||||||||||||||||||||||||||||||||||||
Phenology | Flowering summer in north, year-round in extreme south. | |||||||||||||||||||||||||||||||||||||||||||||||||||||
Habitat | Open plains, rocky hillsides, roadsides, waste ground, railroad ballast | |||||||||||||||||||||||||||||||||||||||||||||||||||||
Distribution |
AL; AR; AZ; CA; CO; CT; GA; IA; IL; IN; KS; KY; LA; MA; MD; MI; MO; MS; NC; NE; NH; NJ; NM; NY; OH; OK; PA; SC; TN; TX; VA; WI; WV; ON; Mexico (Chihuahua, Coahuila, Nuevo León, Tamaulipas); Asia (Japan) [Introduced in Europe]
|
Nearly worldwide; most abundant in tropics; subtropics; and warm-temperate regions; evidently absent from alpine and arctic regions |
||||||||||||||||||||||||||||||||||||||||||||||||||||
Discussion | The current range of Froelichia gracilis is due in large part to its introduction via railroads during the past 100 years, and the majority of records for the species east of the Mississippi River occur on or near railroads. S. F. Blake (1956) discussed this eastern spread of the species. Froelichia gracilis is considered a minor invasive weed in the Northeast; its adaptation to open sandy or gravely soils will restrict its spread to open sites with poor soil. In regions where their ranges overlap, Froelichia gracilis may hybridize with F. floridana. Plants with intermediate form from Texas and the Midwest have been noted. Suspected hybrids appear closest in habit to F. gracilis and will generally key to that species. Floral structure will be intermediate and variable; the branching will be typically less than in F. gracilis and present distal to the base. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Genera ca. 65, species ca. 900 (12 genera, 80 species in the flora). Centers of diversity for Amaranthaceae are southwestern North America, Central America, South America, and Africa south of the Sahara Desert. Generic limits are not well defined in some groups; fewer than 60 or more than 70 genera could be recognized. Some species occur in severe habitats such as sandy, calcareous, gypseous, saline, or serpentine soils in deserts, semideserts, and seashores. Some species are weedy, including the major agricultural weeds in Amaranthus. Some species are cultivated as ornamentals, particularly Amaranthus caudatus (love-lies-bleeding), A. hypochondriacus (prince’s-feather), A. tricolor (Joseph’s-coat), Celosia cristata (cockscomb), and Gomphrena globosa (globe-amaranth). Native Americans domesticated white-seeded grain amaranths (A. caudatus, A. cruentus, and A. hypochondriacus) for use as cereal grains. Some species of Amaranthus and Celosia are potherbs. Amaranthaceae are usually divided into subfamilies Amaranthoideae (anthers 4-locular with two lines of dehiscence) and Gomphrenoideae Schinz (anthers 2-locular with one line of dehiscence). Amaranthaceae and Chenopodiaceae have long been recognized as allied families that share a number of features: generally small flowers, one perianth whorl, a syncarpous gynoecium with a superior ovary and often only one ovule, basal or free-central placentation, pollen characteristics, centrospermous embryo development, betalain pigments, and P-type form (c) sieve-element plastids. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
||||||||||||||||||||||||||||||||||||||||||||||||||||
Key |
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||
Source | FNA vol. 4, p. 445. | FNA vol. 4, p. 405. | ||||||||||||||||||||||||||||||||||||||||||||||||||||
Parent taxa | Amaranthaceae > Froelichia | |||||||||||||||||||||||||||||||||||||||||||||||||||||
Sibling taxa | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
Subordinate taxa | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
Synonyms | Oplotheca gracilis, F. braunii, F. texana, Oplotheca texana | |||||||||||||||||||||||||||||||||||||||||||||||||||||
Name authority | (Hooker) Moquin-Tandon: in A. P. de Candolle and A. L. P. P. de Candolle, Prodr. 13(2): 420. (1849) | Jussieu | ||||||||||||||||||||||||||||||||||||||||||||||||||||
Web links |
|
|