Atraphaxis

Yurtseva, Olga V., Severova, Elena E. & Mavrodiev, Evgeny V., 2017, Persepolium (Polygoneae): A new genus in Polygonaceae based on conventional Maximum Parsimony and Three-taxon statement analyses of a comprehensive morphological dataset, Phytotaxa 314 (2), pp. 151-194 : 184-185

Key to the genera Atraphaxis , Bactria , Persepolium , and Polygonum

1. Perennial or annual herbs, or undershrubs with internodal branching, terminal bracteose inflorescences with tightly congested cymes, perianth of 5 equal-sized or unequal segments, with long filiform basal part of tube. North America ................................... ........................................................................................................................... Polygonum section Duravia subsection Polygonella

— Shrubs, undershrubs or herbs with branches not adnate to stems, inflorescence frondose or bracteose, terminal or lateral, cymes congested or spaced, perianth of 4–5 segments, equal or inner ones strongly enlarged ....................................................................2

2. Annual, rarely perennial herbs with campanulate or urceolate perianth divided to 1/2–5/ 6 in five equal-sized petaloid segments, green along midveins, with wide white or anthocyanin-coloured margin, flat, obtuse, or cucullate and keeled. Ocreas tubular, lacerate or fimbriate, with 5–11 veins. Worldwide....... Polygonum section Polygonum and P. section Duravia subsection Duravia

— Shrubs, dwarf shrubs, or undershrubs, perianth campanulate or urceolate, or with accrescent inner segments and long filiform tube. SW and Central Asia, Eurasia.............................................................................................................................................................3

3. Perianth 6.5–14.5 mm, mostly with four-five unequal segments (two-three inner segments in fruits are much larger than two outer segments), and filiform tube 2.5–7.5 mm long; rarely perianth campanulate, divided to 1/2–3/ 4 in five equal or subequal segments, with tube 1–3 mm long, the filiform basal part of tube no more than 0.4–1.0 mm long. The segments always are petaloid, thin, widen to ends, white or brightly coloured, fully enclosing the achene. Stamens are 6 to 8; styles 2 or 3. Shrubs or undershrubs with compact bracteose, rarely frondulose, terminal or lateral thyrses. Ocreas are 3–10 mm, tubular, with two veins, the upper part membranous, transparent, with two lateral aristate lacinulas connected by finely serrate-incised middle portion. Ocreolas in thyrses are oblique-funnel form, membranous, transparent, with a small herbaceous outgrowth or a narrow keel. Mts of SW and Central Asia, steppes of Eurasia...................................................................................................................................................... Atraphaxis

— Perianth 2.0– 6.5 mm, campanulate or urceolate, with 5(6) equal-sized segments, petaloid or leathery, tube widely funnel-form or cup-shaped, filiform basal part of tube does not exceed 0.3 mm. Stamens 8(9); styles 3. Ocreas lanceolate-tubular, split in two acuminate lacinulas ............................................................................................................................................................................4

4. Dwarf shrubs with shoots never prickly, perianth divided almost to base (4/5–8/10) in 5(6) equal-sized segments petaloid, glabrous, with papillae only at segment edge. Pamir, Tian-Shan............................................................................................................. Bactria

— Dwarf shrubs, undershrubs, or herbs, some with prickly shoots, with perianth divided to 1/2–3/4, fully puberulent or glabrous, at last case without papillae at segment edge .........................................................................................................................................5

5. Caespitose undershrubs, or dwarf shrubs, some with prickly shoots. Perianth urceolate or campanulate, 2–6 mm long, fully densely shortly puberulent, divided to 2/3–3/ 4 in oblong-elliptical or ovate segments, gradually narrowed to the top, leathery (coriaceous), rigid, purplish-green, with narrow (less than 0.2 mm) membranous margin. Ocreas are 3–7 mm long, truncate-tubular or acuminate-tubular, membranous, shortly bidentate, later bilacerate, without veins, or with 2–6 veins. Endemics of Iran.............. Persepolium

— Small shrubs, undershrubs, or herbs, shoots not prickly. Perianth urceolate, 2–3 mm, glabrous or papillate at tube, divided to 1/2–3/4, segments petaloid, green with wide white or anthocyanin-coloured margin, flat, obtuse, or keeled and cucullate. Ocreas are 3–10 mm, tubular, membranous, with 5–11 veins, lacerate-fimbriate. Mts of SW and Central Asia ............................................ ........................................................................................................................................................ Polygonum section Pseudomollia