Perideridia americana (Nutt.) Reichenb.
Family - Apiaceae
Stems - To 1m tall, herbaceous, from a thickened roots, typically simple but sometimes branching in apical half, glabrous, erect.
Leaves - Alternate, pinnately to ternately divided, petiolate. Petiole flat, involute, sheathing, expanded, 1cm broad when unrolled. Blades to 16cm long, 8-9cm broad. Ultimate leaf divisions linear, entire, to 2-3mm broad.
Inflorescence - Compound umbel with +/-20 rays subtended by 0-4 linear bracts. Rays to +10cm long. Bracts to 2-3cm long. Raylets +/-20, to +1.5cm long. All glabrous.
Flowers - Petals 5, spreading, white, glabrous, curled at apex, clawed, 1.3mm broad, 2.5mm long(uncurled). Stamens 5, alternating with the petals, spreading. Filaments white, to 2mm long. Anthers pale yellow to white, .2mm long. Styles 2, white, expanded at base into stylopodium. Ovary green, inferior, 2mm long, 1.1mm broad, glabrous. Sepals 5, alternating with the petals, .5mm long, green. Fruit to 6mm long, oblong to ovate, glabrous.
Flowering - April - July.
Habitat - Rocky open woods, on limestone and chert substrata, bluffs, glades.
Origin - Native to U.S.
Other info. - This lanky species can be found in the scattered throughout portions of Missouri but is most common in the southwest. The plant is completely glabrous and is rarely branched. The thick roots typically form in fascicles.
Photographs taken at Prairie State Park, Barton County, MO., 6-23-00.