By: Til K. Thapa and Sangeeta Rajbhandary

Perennial rhizomatous herbs, with fibrous rootstock or creeping. Stems simple, unbranched and cylindric with simple leaves in a whorl of 3–12. Leaves, linear to oblanceolate, flat and grass-like or ensiform, distichous and petiolate. Inflorescence a terminal, spike-like raceme on leafless scape. Flowers terminal, bisexual, hypogynous or semi-epigynous, actinomorphic, solitary or spike, bracts and bracteoles present or absent. Perianth 3–10-merous in two whorls, segments (tepals) free or fused to ovary below, with all segments similar or outer sepaloid and inner petaloid or filiform. Stamens 6 or equal in number of tepals, filaments free, anthers basifixed, dehiscence inwards or outwards, connectives sometimes prolonged upward. Ovary superior, 1- or 3-locular, apex sometimes with thickened rim, style fused or separated into stigmatic lobes; ovules many per locule. Fruit a berry or capsule. Seeds sometimes with fleshy sarcotesta or often with terminal projections.

Worldwide 17 genera and 173 species (Christenhusz et al., 2017). Three genera and 6 species in Nepal.

Key to Genera

1 a Leaves in a basal rosette. Flowers in a spike …………………………………………………………..    1. Helonias

b Leaves in a whorl near top of stem. Flower solitary……………………………………….…………….…………..…2

2 a Leaves three per whorl. Outer and inner tepals similar …………………………………………….. .2. Trillium

b Leaves more than three per whorl. Outer and inner tepals different …………………..…………. 3. Paris