Plectocephalus

Penneckamp, Diego, Chaura, Rodrigo, Rojas, Gloria & Stuessy, Tod, 2020, Taxonomic notes on Plectocephalus (Centaurea s. l., Centaureinae, Asteraceae) from Chile, including new combinations and synonyms, Phytotaxa 437 (4), pp. 227-236 : 233-234

Key to the species of Plectocephalus in Chile

1. Plants unbranched with a terminal, solitary, sessile capitulum ........................................................... Plectocephalus monocephalus

1. Plants branched with several capitula.................................................................................................................................................2

2. Plants rhizomatous; flowering stems with linear entire leaves .................................................................... Plectocephalus bulbosus

2. Plants not rhizomatous; flowering stems with divided leaves............................................................................................................3

3. Stems tomentose to woolly-pubescent ...............................................................................................................................................4

3. Stems glabrous or glabrescent ............................................................................................................................................................7

4. Leaves crenulate-dentate; corollas yellow or yellow-pink............................................................................ Plectocephalus gayanus

4. Leaves divided, pinnatifid; corollas whitish or pink ..........................................................................................................................5

5. Phyllaries with appendage colorless at the center, glabrous or glabrescent; leaves deeply pinnatisect with narrow linear segments ................................................................................................................................................................... Plectocephalus illapelinus

5. Phyllaries fimbriate, with appendage black or blackish at the center, pubescent; leaves pinnate or pinnatifid with acute lanceolate segments .............................................................................................................................................................................................6

6. Capitulum 2 cm or less in diameter; phyllaries in 4–5 series; flowering stems with many leaves below the capitula........................ ................................................................................................................................................................ Plectocephalus atacamensis

6. Capitulum more than 2 cm in diameter; phyllaries in 6–7 series; flowering stems with few leafy bracts or reduced leaves below the capitula ........................................................................................................................................................ Plectocephalus floccosus

7. Capitulum borne sessile in the flowering branch ................................................................. Plectocephalus chilensis var. brevilobus

7. Capitulum borne in a pedunculate flowering branch .........................................................................................................................8

8. Leaves deeply pinnatisect with narrow linear segments .............................................................................. Plectocephalus bridgesii

8. Leaves pinnate or pinnatifid with acute lanceolate segments ............................................................................................................8

9. Adult leaves 1.5–2.5 cm long; capitulum 1–1.5 cm in diameter.......................................................... Plectocephalus cachinalensis

9. Adult leaves more than 5 cm long; capitulum 2–4 cm in diameter....................................................................................................9

10. Leaves glabrous on abaxial surface.............................................................................................................. Plectocephalus chilensis

10. Leaves puberulent on abaxial surface........................................................................................................... Plectocephalus formosus