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Conyza L.

假蓬屬

SOEJIMA, Akiko & PENG, Ching-I

Conyza canadensis var. pusilla

Credit: HAST

Annual or perennial herbs, rarely shrubs or small trees. Leaves alternate, usually oblanceolate, entire to dentate or pinnately lobed. Heads heterogamous, rather small, several to numerous in corymbs or panicles, rarely solitary, disciform or rarely short radiate. Receptacle flat or subglobose, naked or alveolate. Involucre campanulate to somewhat urceolate, bracts 2-4 seriate, more or less imbricate, scarcely herbaceous, soon widely spreading. Florets numerous, corolla very slender. Outer florets pistillate, numerous in many rows, corolla tubular, filiform; sometimes with a narrow, white or purplish, minute ligule, surpassed by pappus; style branches nearly linear, nearly glabrous to glandular puberulent. Disc florets bisexual, or sometimes partly functionally staminate, usually few, tubular, (4-)5-lobed. Achenes obovoid-oblong, sometimes compressed, mostly pubescent. Pappus of many, fine, mostly fragile bristles.

About 60 species, mainly tropical and subtropical, in both the Old and New Worlds. In Taiwan, six species, one of which is represented by two varieties.


KEY TO SPECIES

1 Leaf base or petiole clearly amplexicaul.   (2)
+ Leaf base not amplexicaul.   (3)
       
2 (1) Radical leaves withered at anthesis; leaves pinnately cleft; heads more than 1 cm across.   Conyza aegyptiaca
+ Radical leaves persistent at anthesis; leaves dentate; heads less than 1 cm across.   Conyza japonica
       
3 (1) Corolla of outer florets less than half as long as styles and pappus.   Conyza leucantha
+ Corolla of outer florets nearly equalling styles and pappus.   (4)
       
4 (3) Heads ca. 2.5-3.5 mm across, ligules small but apparent.   (5)
+ Heads ca. 5-8 mm across, ligules obscure.   (6)
       
5 (4) Stems hirsute; leaves lanceolate, serrate.   var. canadensis
+ Stems glabrate; leaves linear, nearly entire.   var. pusilla
       
6 (4) Leaves linear to linear-lanceolate; axillary branches usually overtopping axis.   Conyza bonariensis
+ Leaves oblanceolate; axillary branches not overtopping main axis.   Conyza sumatrensis

Lower Taxa

Related Synonym(s):


 

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