3. Anulocaulis leiosolenus (Torrey) Standley, Contr. U.S. Natl. Herb. 12: 375. 1909.
Boerhavia leiosolena Torrey in W. H. Emory, Rep. U.S. Mex. Bound. 2(1): 172. 1859 (as Boerhaavia)
Herbs, stout perennial. Stems 0.5-1.5 m. Leaves: 1-3 pairs near base; petiole 3-7 cm; blade broadly ovate to almost round, 5-15 × 4-19 cm, base cordate, rarely rounded, apex rounded or broadly obtuse, adaxial surface dull green to pale green, abaxial surface grayish green, often very pale, both surfaces glabrous or sparsely villous with fine hairs with pale brown or blackish pustulate bases. Flowers borne singly or in ill-defined clusters of 2-5 on branches of inflorescence; perianth 25-35 mm, tube greenish bronze, limbs white, pink, or rose-pink, abruptly flared from tube, glabrous or minutely pubescent externally at edge (pubescence most easily seen at tip of mature bud); stamens 3, exserted 25-40 mm. Fruits biturbinate, 4.2-8 × 2.6-4.6 mm, secreting mucilage when wetted; ribs 10, narrow, undulate; equatorial flange well developed, sinuate.
Varieties 4 (4 in the flora): sw North America.
Anulocaulis leiosolenus occurs as isolated, islandlike populations that are homogeneous within but differ slightly between populations. The turbinate fruits with prominent ribs and equatorial flange ridge, and the long-tubular perianths, are unifying features. Pubescence, when present, is inconspicuous on the perianth, and is best seen on tips of mature buds.