6. Trillium viride Beck (green trillium)

Pl. 108 f; Map 442

Aerial stems 22–40 cm long. Leaves 8–12(–15) cm long, usually about 2 times longer than wide, narrowly to broadly elliptic, the tips rounded or pointed, but not acuminate, sessile, often somewhat mottled, the upper surface with numerous, evenly distributed stomates (appearing as tiny, white speckles under magnification). Flowers erect, sessile. Sepals spreading to ascending at flowering, 30–50 mm long, lanceolate, rarely purplish tinged. Petals (31–)40–60 mm long, erect or nearly so, oblanceolate to nearly linear, broadest above the middle, narrowed to a stalklike base 7–15 mm long, green to yellowish green, sometimes purplish tinged throughout or more commonly toward the base. Stamens 16–24 mm long, less than half as long as the petals. Ovary with 6 angles or wings in the upper half. Fruits erect. 2n=10. April–June.

Scattered in the eastern half of Missouri, both north and south of the Missouri River (Illinois, Missouri). Mesic upland forests in ravines or valleys and stream banks, usually on calcareous substrates.

The flowers of this species have a musty or spicy odor similar to that of rotting apples. It is the only species of Trillium in Missouri with numerous stomates on the upper leaf surface. These are visible as tiny white specks under a hand lens.

The separation of T. viride from the closely related T. viridescens remains somewhat controversial. Steyermark (1963) discussed his inability to discriminate consistently between plants from populations in the eastern and western parts of the state, but he was unaware of the stomatal character that has been used to differentiate the two taxa. Freeman (1975) characterized T. viridescens as a somewhat more robust species than T. viride and occurring to the west of the latter taxon. He compiled several additional characters to distinguish the two, aside from the stomates. Trillium viride was characterized as having leaf tips rounded to pointed and nonacuminate (vs. sharply pointed to acuminate) and stigmas that are ascending and rarely spreading between the erect stamens (vs. widely spreading and extending between the erect stamens). However, the presence of occasional plants with ambiguous leaf shapes in populations otherwise ascribable to one or the other taxon and the discovery in 1992 of a disjunct population of T. viridescens in Jefferson County lend weight to the opinions of some botanists who would prefer the two taxa to be recognized as varieties or subspecies of T. viride, or not to segregate T. viridescens at all. In spite of the fact that the two taxa appear somewhat different in the field to those who have seen them, the most reliable morphological character to distinguish between them appears to be the distribution of stomates on the leaves, as noted above. Further research is necessary to document the degree of genetic differentiation between these cryptic entities.

Steyermark (1963) and Freeman (1975) have discussed the distinctions between T. viride and T. luteum (Muhl.) Harbison of the southeastern United States. Reports of the latter species from Missouri were dismissed by Steyermark (1963) based upon redetermination of the pertinent specimens.