Spermolepis inermis (Nutt. ex DC.) Mathias & Constance
Western Scaleseed, Red River Scaleseed
CC = 3
CW = 5
MOC = 24
Family - Apiaceae
Habit - Annual forb.
Stems - Ascending to erect, to 60 cm, usually branched, glabrous, ridged.
Leaves - Alternate, compound, short-petiolate or more commonly sessile. Sheathing bases not or only slightly inflated. Leaf blades 1-5 cm long, oblong to oblong-ovate in outline, pinnately 2-4 times dissected, the usually numerous ultimate segments 1-25 mm long, narrowly linear to threadlike.
Inflorescences - Terminal and axillary, compound umbels, short-to more commonly long-stalked. Involucre absent. Rays 5-11, 1-13 mm long, unequal in length, strongly ascending, straight, the central umbellet of most umbels sessile or nearly so and 1-3-flowered. Involucel of 1-3 bractlets, these mostly shorter than the flower stalks, linear, the margins sometimes minutely toothed. Flowers 1-6 in each umbellet.
Flowers - Sepals absent. Petals oblong to ovate, rounded at the tip, white. Ovaries and fruits glabrous and roughened with dense, minute tubercles.
Fruits - Schizocarps 1.5-2.0 mm long, ovate in outline, flattened laterally, slightly narrowed along the commissures, glabrous, roughened with dense minute tubercles, the mericarps with 5 inconspicuous, narrow, rounded ribs.
Flowering - May - June.
Habitat - Sand prairies, upland prairies, glades, fields, roadsides, and railroads.
Origin - Native to the U.S.
Lookalikes - Other species of Spermolepis.
Other info. - This plant is easily missed. Its flowers are tiny and inconspicuous and its foliage sparse and wispy. It is found in scattered locations in Missouri, predominantly in the south and west portions of the state. Its larger distribution is mostly within the south-central continental U.S. and extends into Mexico. The plant is easily identified as a species of Spermolepis by the sheathing, highly dissected leaves and compound umbels of tiny white flowers. The ovaries and fruits are roughened with dense tubercles but lack hairs or bristles.
Photographs taken at Sand Prairie Conservation Area, Scott County, MO, 5-22-2022, and at the Edgar W. Schmidt Sand Prairie, Scott County, MO, 5-22-2022 (SRTurner).