Perennial herbs with narrow equitant 2-ranked leaves and perfect regular or irregular mostly clustered flowers subtended by bracts. Perianth of 6 segments or 6-lobed, its tube adnate to the ovary, the segments or lobes in two series, convolute in the bud, withering-persistent. Stamens 3, inserted on the perianth opposite its outer series of segments or lobes; filaments filiform, distinct or united; anthers 2-celled, extrorse. Ovary inferior, mostly 3-celled; ovules mostly numerous in each cell, anatropous; style 3-cleft, its branches sometimes divided. Capsule 3-celled, loculicidally dehiscent, 3-angled or 3-lobed (sometimes 6-lobed), many-seeded. Seeds numerous, in 1 or 2 rows in each cavity of the capsule. Endosperm of the seed fleshy or horny; embryo straight, small.

About 57 genera and 1000 species, of wide distribution, in temperate and tropical regions of both hemispheres.

Style-branches opposite the anthers, very broad, petal-like.

Style-branches alternate with the anthers, slender or filiform.

1.

Iris.

Style-branches 2-cleft; plants bulbous.

2.

Nemastyiis.

Style-branches undivided; plants not bulbous.

Filaments all distinct; seeds fleshy.

3.

Gemmingia.

Filaments united; seeds dry.

4.

Sisyrinchium.