Araceae

By: Nawal Shrestha, Himanchal T. Magar, Mohan Siwakoti & Krishna K. Shrestha

Taxon Description 

Perennial herbs, terrestrial to aquatic, often with tubers, rhizomes or corms, vines with aerial roots, epiphytes or free-floating, sometimes thallose aquatics. Leaves alternate, simple, blade often well developed, sometimes strongly lobed, pinnately to palmately compound, usually entire, with parallel, pinnate or palmate venation, sheathing at base; stipules absent, but glandular hairs or small scales present at the node inside the leaf sheath. Inflorescences indeterminate, usually terminal, forming a spike of numerous small flowers densely set on a fleshy spadix often with an apical appendix, and subtended by a large leaf-like to petal-like bract (spathe), but inflorescence much reduced in floating aquatic taxa. Flowers bisexual or unisexual (plants usually monoecious), radial, lacking individual bracts. Tepals usually 4–6 or absent, sometimes inconspicuous, distinct to connate, and often fleshy, valvate or imbricate. Stamens 1–6(–12), filaments distinct to connate; anthers sometimes opening by pores, distinct to connate. Carpels usually 2 or 3, connate. Ovary superior, stigma 1, punctuate or capitate. Nectaries absent. Fruit usually a berry.

Taxon Statistics

Worldwide 118 genera and ca. 3,300 species in tropical and subtropical regions. More common in tropical forests and wetlands. Fifteen genera and 42 species in Nepal, in tropical to subalpine regions between 300–4300 m.

Number of genera and species in the family, and number of species in the genera are cited from the ‘Flowering plants of the World’ (Christenhusz et al., 2017).

Key to Genera

1a Underground stems present ………………………..………………………….…………………………………………………………………………………………………………………………………………….….………. 2

b Underground stems absent …………………………………………………………………………………………………………………………………..………………………………………….….………..…….……………. 10

2a Plants rhizomatous, with prickly spines on all parts ………………………………………………………………………………………………………………………………………………………………….6. Lasia

b Plants rhizomatous, cormose or tuberous without prickly spines ……………………………………………………………….….……………………………………………………………………….……..…… 3

3a Plants tuberous ……………………………………………………………………………………………………………………………….….……………………………………………………………………………………………..4

b Plants rhizomatous or cormose ………………………………………………………………………………………….….………………………………………………………………………….………………………………… 5

4a Leaves simple, entire …………………………………..……………………………………………………………….….……….…………………………………………………………………………………………… 3. Ariopsis

b Leaves compound, pinnately dissected ………………….……………………………………………………………….….……………………………………………………………………………. 2. Amorphophallus

5a Leaves palmately, radiately or pedately dissected. Spathe tube-like, forming a distinctive drooping or erect hood above the spadix…………………………….… 4. Arisaema

b Leaves hastate, cordate, lobed or pedate. Spathe not tube-like, and not forming a hood above the spadix ………..……………………………………………………….….………….……… 6

6a Leaves hastate or lobed or pedate ……………………………….…………………….…………………………………………………………………………………………….….……….……………………………………. 7

b Leaves cordate, sagittate, entire or ova..………………………………………………………………………………………………………………………….….………..………………….………..…………………………. 8

7a Margin at the base of spathe overlapping but not fused. Leaves produced with inflorescence………………………………………………………….….…………..…………. 15. Typhonium

b Margin at the base of spathe fused to form tube. Leaves produced after inflorescence…………………………………………………….….………..……………..……………  12. Sauromatum

8a Stolons with scarious deciduous cataphylls …………..……………………………………………………………………………………………………….….…………………………………………..  10. Remusatia

b Stolons absent ……………………………………..………………………………………………………………………………………………………………………….….………..……………………………………………..……….. 9

9a Wax glands present in axils of primary lateral veins and midrib. Inflorescence paired. Fruit brightly colored, odorless………………………………………….….……….. 1. Alocasia

b Wax glands absent. Inflorescence numerous. Fruit inconspicuously colored, smelly …………………………………..……………………………………………….………..……..……. 5. Colocasia

10a Free-floating aquatic plants. Leaves minute or up to 10 cm long …………………………………………………………………………………………….….………..………………………….…………….. 11

b Terrestrial, climbing plants. Leaves more than 10 cm long …..……………….…..…..…………….…..……………………………………………………………….….…………….…..………………………… 13

11a Plants with simple and rosette leaves, 1.3–10 X 1.5–6 cm  ..………………………….…..……………………….…..…………………………………………………….….……………………………. 8. Pistia

b Plants thallose, 0.4–6 X 0.5–7 mm …………………………….…..……………………….…..……………………….…..……….………………………………………….….………….…………………………………….. 12

12a Thallus with (5–)7–21 roots. Veins 7–16(–21) …….…………………….…..……………………….…..……………………………………………….….……………………………………………… 14. Spirodela

b Thallus with a single root. Veins 1–5(–7) ……………………………….…..……………………….…..…………………………………………………….….………………….……….…………………………. 7. Lemna

13a Petiole winged. Leaves entire ………………………………….……………….…..……………………….…..…………………………………………….….………………………….…….…………………….. 9. Pothos

b Petiole unwinged. Leaves entire or pinnately dissected …….…………….…………….…..……………………………………………………………….….……….…..……………………………………………. 14

14a Leaves entire …………………………………………………………….…..……………………….…..………………….……………………………………………….………………………………………….. 13. Scindapsus

b Leaves pinnately dissected …………..……………………….…..……………………….…..……………………….………………………………………….….………..…………..…….……….….. 11. Rhaphidophora