Colocasia, Schott (1832: 18), Schott, 1832

Matthews, Peter J., Nguyen, Van Du, Fang, Qiong & Long, Chun-Lin, 2022, Colocasia spongifolia sp. nov. (Araceae) in southern China and central Vietnam, Phytotaxa 541 (1), pp. 1-9 : 7-8

Identification key

1. Plants with stolons; stem short to tuberous and decumbent, or rhizomatous; with multiple adaxial buds in each leaf axil; spadix with sterile appendix or not; staminodes between ovaries many to abundant ...................................................................... 2

- Plants without stolons or side-tubers; stem cylindrical, erect; a single adaxial bud in each leaf axil; spadix always with sterile appendix; staminodes between ovaries few or absent........................................................................................................................6

2. Sterile appendix long (up to ca. 10 cm,> 2x length of male zone), thick, diam. up to 10 mm at base (wider than male zone) ......... ........................................................................................................................................................................................ C. formosana

- Sterile appendix short and slender, much reduced, or completely absent ..........................................................................................3

3. Sterile appendix short (length 3.5 cm, equal to male zone), slender conical, diam. 5 mm at base (more narrow than male zone); underside of leaf blade surface pilose, main and primary lateral veins pubescent; petiole and peduncle pubescent .......................... ..................................................................................................................................................................................... C. menglaensis

- Sterile appendix absent or much reduced; underside of leaf blade pubescent over whole surface, or not; petiole and peduncle not pubescent ............................................................................................................................................................................................4

4. Plant stout, petiole maximum 55 cm long; stem short (< 2 cm long, 3 cm diam.; sub-globose); inflorescence appears with leaves; peduncle little shorter than petiole .......................................................................................................................... C. gaoligongensis

- Plant tall, 50–100+ cm long; stem sub-globose to elongate, decumbent, minimum 2 cm long; inflorescences appear after leaf emergence; peduncle much shorter than petiole.................................................................................................................................5

5. Blade cordate-ovate, upper surface waxy, not glossy green, often with dark purple patches; interprimary veins very prominent on underside of mature blade; sterile appendix absent (a much reduced vestige, apiculate, < 1cm); staminodes between ovaries abundant, with flask shape and discoid apex............................................................................................................... C. yunnanensis

- Blade cordate-sagittate, overall elongate-triangular with deep sinus, upper surface not waxy (wettable), glossy green, without purple patches; interprimary veins inconspicuous to slightly raised on underside of mature leaf; sterile appendix completely absent; staminodes between ovaries abundant, obovate with rounded apex ................................................................................ C. lihengiae

6. Leaf blade oblong-ovate, posterior lobes narrow and rounded; underside of blade pubescent over whole surface, including primary veins; peduncle cylindrical........................................................................................................................................... C. kachinensis

- Leaf blade cordate-ovate; posterior lobes broad and rounded; no parts pubescent; peduncle three-angled ......................................7

7. Plant very large, petiole 90–140 cm; stem erect or nearly erect, 120–135 cm long, 12–18 cm diam.; leaf blade with distinctly indented sinus, main vein and primary lateral veins purple, lamina “membranous”; peduncle green or purple; spathe ca. 33 cm long, spathe blade yellow with purple margin, almost erect or sometimes reflexing at anthesis; spadix ca. 30 cm long, little shorter than spathe ............................................................................................................................................................................. C. gongii

- Moderate sized plant, petiole up to 120 cm, stem erect or decumbent with erect apex, up to 14 cm long, 5.5 cm diam.; leaf blade with shallow sinus, main vein and primary lateral veins green; lamina thick, rubbery, smooth on underside; peduncle green; spathe up to 19 cm long, spathe blade yellow without purple margin, strongly reflexed at anthesis; spadix 10–14 cm long, much shorter than spathe ..................................................................................................................................................................... C. spongifolia