1. Parietaria pensylvanica Muhl. ex Willd. (Pennsylvania pellitory, pellitory)

P. pensylvanica var. obtusa (Rydb. ex Small) Shinners

Pl. 572 d, e; Map 2672

Plants annual, unarmed, finely and often densely pubescent with minute, nonstinging hairs (the leaves sometimes, except for the margins, glabrous or nearly so), the hairs at least in part curved and/or hooked, usually with a short taproot, rarely sparse, longer, spreading hairs also present. Stems 5–40(–60) cm long, variously erect to loosely ascending, often weak and reclining on other vegetation or the ground, unbranched or branched. Leaves alternate, short-petiolate, lacking stipules. Leaf blades 1–7 cm long, narrowly to broadly lanceolate, oblong-lanceolate, ovate, oblong-ovate, or somewhat rhombic, mostly narrowly angled at the base, narrowly angled to tapered at the tip, the margins entire, with 3 main veins (the lateral pair branching above the blade base); cystoliths rounded. Inflorescences axillary, small, sessile clusters, the perfect and pistillate flowers usually more or less mixed in the same cluster. Bractlets 3.5–5.0 mm long, longer than the calyces, linear to narrowly oblong, 2–6 bractlets forming an involucre around each cluster. Staminate flowers usually absent, the perfect flowers with 4 sepals, these 1–2 mm long, ascending to slightly incurved at the tips. Stamens 4. Pistillate flowers with 4 sepals fused to about the midpoint, these 1.5–2.0 mm long, equal. Style absent or minute, the stigma capitate (papillose and appearing bushy, not persistent at fruiting). Fruits 0.9–1.2 mm long, symmetrically attached at the tip of a short, basally expanded stalk, flattened, the body ovate in outline, the surface smooth, tan to yellowish brown. 2n=14, 16. May–October.

Scattered nearly throughout the state (nearly throughout the U.S.; Canada, Mexico). Glades, bases, ledges, and tops of bluffs, savannas, mesic to dry upland forests, and banks of streams and rivers; also fencerows, gardens, railroads, roadsides, and open disturbed areas.

Uncommon plants with slightly denser pubescence and slightly shorter involucres, as well as sometimes also slightly blunter leaf tips, have been called var. obtusa. This variant intergrades freely with the more typical form (Boufford, 1997b).

During his studies of the genus Parietaria in the United States and Canada, B. D. Hinton (1968a) discovered an unusual specimen collected by John Kellogg in 1913 near Jerome (Phelps County) that he determined to be P. praetermissa B.D. Hinton. This species, which formerly was known under the misapplied name P. floridana Nutt. (B. D. Hinton, 1968b), is otherwise endemic to the Atlantic and Gulf Coastal Plains from North Carolina south to Florida and west to Louisiana (B. D. Hinton, 1968a; Boufford, 1997b). During his studies for the flora of North America Project, Boufford (1997b) confirmed this determination, but doubted the occurrence, suggesting that the specimen must be mislabeled. Parietaria praetermissa occurs mainly in coastal areas near sea level and it is very unlikely that a chance introduction into Missouri would survive for very long. Thus, the species is excluded from the Missouri flora for the present. However, botanists working in disturbed, sandy areas of central Missouri should keep watch for unusual specimens of pellitory. Parietaria praetermissa differs from P. pensylvanica very subtly; its fruits have the apical point and basal attachment point positioned slightly off-center (vs. symmetrically in P. pensylvanica) and its perianth is slightly longer (1.7–2.3 mm).