Glabrous erect unbranched herbs, with short scarred rootstocks and 3 leaves whorled at the summit of the stem, subtending the sessile or peduncled solitary bractless flower. Solitary long-petioled leaves are sometimes borne on the rootstock. Perianth of 2 distinct series of segments, the outer 3 (sepals) green, persistent, the inner 3 (petals) white, pink, purple or sometimes greenish, deciduous or withering. Stamens 6, hypogynous; filaments short; anthers linear, mostly introrse. Ovary sessile, 3-6-angled or lobed, 3-celled; ovules several or numerous in each cavity; styles 3, stigmatic along the inner side. Berry many-seeded. Seeds horizontal. [Latin, in allusion to the 3-parted flowers and the 3 leaves.]

About 24 species of North America and Asia. Besides the following, some 7 others occur in southern and western North America. Known as Three-leaved Nightshade and Birthroot. Phyllody, i. e., the reversion of petals or sepals to leaves, is occasional, and the floral parts are sometimes in 4's. Type species: Trillium cernuum L.

Flower sessile.

Leaves sessile; sepals not reflexed.

Flowers purple; petals lanceolate.

1.

T. sessile.

Flowers green; petals linear.

2.

T. viride.

Leaves petioled; sepals reflexed.

3.

T. recurvatum.

Flower peduncled.

Leaves oval or ovate, obtuse or obtusish, 1'-2' long.

4.

T. nivale.

Leaves broadly ovate or rhombic, acuminate, 2'-7' long.

* Leaves sessile, or narrowed at the base and short-petioled.

Petals obovate or oblanceolate, 1 1/2'-2 1/2' long.

5.

T. grandiflorum.

Petals ovate or lanceolate, 1/2'-1 1/2' long.

Peduncle 1 1/4'- 4' long, erect or declined; petals spreading.

Petals brown-purple, rarely white; filaments two-thirds as long as the anthers,

or longer.

6.

T. erectum.

Petals white; filaments not more than half as long as anthers.

7-

T. declinatum.

Peduncle 1 1/4' long or less, recurved; petals recurved.

8.

T. cerniium.

** Leaves distinctly petioled, obtuse or rounded at the base.

9.

T. undtilatum.

2 Trillium L Sp Pi 339 1753 1299