|
(Last Modified On 6/6/2013)
|
|
|
|
(Last Modified On 6/6/2013)
|
|
Genus
|
Conyza Less.
|
|
PlaceOfPublication
|
Syn. Gen. Comp. 203. 1832, not L.; nom. cons.
|
|
Note
|
TYPE: C. chilensis Spreng.
|
|
Synonym
|
Leptilon Raf., Amer. Monthly Mag. & Crit. Rev. 2: 268. 1818. TYPE: Erigeron divaricatus Michx. Erigeron sect. Caenotus Nutt., Gen. N. Amer. P1. 2: 148. 1818. LECTOTYPE: E. canadensis L. Laennecia Cass., Dict. Sci. Nat. 25: 91. 1822. LECTOTYPE: L. gnaphalioides (Kunth) Cass. = Conyza gnaphalioides Kunth. Caenotus (Nutt.) Raf., Fl. Tell. 2: 220. 1836. "Coenotus" auct., orth. mut., not Nutt.
|
|
Description
|
Annual or perennial herbs, rarely shrubby, our species erect and not truly rosette forming. Leaves alternate, simple, entire to pinnatisect, pubescent or glabrous. Inflorescence mostly of many heads in an open or compact panicle or sometimes racemose or subspicate along the terminal portion of the main stem, rarely of few or solitary heads; leaves of the flowering portion. often smaller and of different shape from those lower on the stem. Heads disciform; involucral bracts imbricate in 1-several series with a herbaceous midvein and a hyaline margin, this usually contracted before the apex; receptacle naked, flat to slightly convex, smooth or muricate, sometimes darkened; outer florets numerous in many series, the corolla apices denticulate or minutely ligulate, the style branches exserted, linear, glandular-verrucose; inner florets fewer than the outer florets, narrowly tubular, differentiated about mid-length into a tube and limb, the limb tubular, apically 5-dentate, the anthers basally rounded or obtuse, the appendages narrowly lanceolate to subulate, the style branches flattened with a thickened margin, dorsally papillose, its appendages triangular. Achenes uniform, much compressed, the margins thickened by two nerves, glabrous to pubescent; pappus of fine strigulose bristles in one or more series, the inner bristles about the length of the inner florets, the outer bristles when present shorter than the achene itself.
|
|
Habit
|
herbs
|
|
Note
|
Conyza is distinguished from Erigeron by its short or absent ligules. It is included in Erigeron by many botanists. The florets are usually white or yellowish but in some species may be brownish. The genus is primarily pantropical with about 60 species, but some species are native to the temperate zones, and a few tropical species are wide ranging into temperate areas. Many species are troublesome weeds of towns and cultivation. "Horseweeds." Conservation of the name Conyza Less. (Astereae) with the type C. chilensis over Conyza L. (Inuleae) and its type C. squarrosa L. resulted in a major reconstruction; many Old World species of Conyza L. have been or must be transferred to other genera as they are not congeneric with Conyza Less.
|
|
Common
|
Horseweeds
|
|
Reference
|
Marshall, J. B. & D. McClintock. 1972. Conyza in Britain. Watsonia 9: 201- 202. 1972.
|
|
Key
|
a. Inflorescence an open panicle; pedicels elongate and slender, glabrate to puberulent. b. Lower leaves mostly scabrous, the teeth when present obtuse or rounded apically; receptacle 4-6 mm across; outer floret with a distinct ligule ...... 1. C. apurensis bb. Leaves not scabrous, the teeth when present with pointed tips; receptacle less than 3 mm across; outer floret with or without a ligule. c. Outer florets with a distinct but minute ligule 0.5 mm long; receptacle 1-1.5 mm across; upper leaves linear, glabrate ...... 3. C. canadensis cc. Outer florets apically dentate without a distinct ligule; receptacle 2-2.5 mm across; upper leaves narrow but not linear, mostly pubescent ...... 2. C. bonariensis aa. Inflorescence compacted or crowded in clusters or spikelike racemes; pedicels short and stout, lanate or tomentose. d. Lower leaves small (to 3 cm) and divided nearly to the margin into 3-7 teeth; stems arachnoid to lanate with soft, wispy hairs; inner florets less than 5, mm long, tubiform with a deeply cleft limb; achene with an irregular ring of glands near the apex ...... 5. C. schiediana dd. Lower leaves larger than 3 cm, toothed or crenate but not deeply divided; stems puberulent to tomentose with dense spreading hairs; inner florets more than 5 mm long, tubular, the lobes not twice as long as wide; achene without glands ...... 4. C. chilensis
|
|
Tag
|
|
|
|
Project Name
|
|
Tag
|
|
|
|