Taxonomy of the Polygonum douglasii (Polygonaceae ... - WLU

12 BRITTONIA
[VOL. 57
Key to the Polygonum douglasii complex
1. Pedicels patent or erect.
2. Leaves with one pleat on each side of the midvein --------------------------------------------------------------------------------- P. tenue
2. Leaves not pleated.
3. Ocreae 1–4 mm long, funnelform; perianth 1.8–2.5 mm long; achenes 1.8–2.3 mm long.
4. Plants 1.5–3.5 cm tall; leaves and bracts uniformly papillose, cylindrical due to revolute margins
that join together on the abaxial face ---------------------------------------------------------------------------------------- P. utahense
4. Plants 3–50 cm tall; leaves and bracts glabrous or papillose only on the margins; leaves plane
or with narrow revolute margins, which are never joined together on the abaxial face.
5. Plants glabrous; flowers wide-open ------------------------------------------------------------------------------------ P. cascadense
5. Plants papillose-scaberulous at least on the ocreae; flowers closed or semiopen.
6. Leaves elliptic, obovate to subround, pure green adaxially, margins plane or narrowly
revolute, irregularly thickened or denticulate-papillose; anthers 120–165 �m long ----
-------------------------------------------------------------------------------------------------------------------------------------------- P. minimum
6. Leaves linear to narrow elliptic, � glaucescent adaxially, margins revolute, smooth;
anthers 250–325 �m long ---------------------------------------------------------------------------------------------- P. nuttallii
3. Ocreae 4–12 mm long, not funnelform; perianth 3–5 mm long; achenes 2.5–5 mm long.
7. Inflorescence dense, cymes crowded and overlapping at stem and branch apices; anthers
400–550 �m long ---------------------------------------------------------------------------------------------------- P. spergulariiforme
7. Inflorescence open, cymes regularly spaced along stem and branches; anthers 130–200 �m
long ----------------------------------------------------------------------------------------------------------------------------------- P. sawatchense
8. Stems and ocreae glabrous; leaf blades linear to linear-lanceolate, smooth on the margins.
-------------------------------------------------------------------------------------------------- P. sawatchense subsp. sawatchense
8. Stems and ocreae scaberulous-papillose; leaf blades elliptic or elliptic-lanceolate, denticulate-papillose
on the margins --------------------------------------------- P. sawatchense subsp. oblivium
1. Pedicels reflexed.
9. Ocreae 6–12 mm long; flowers and achenes 3–5 mm long.
10. Flowers wide-open or semiopen; pedicels 0.5–1 mm long; perianth tube 9–17% of the
perianth length; anthers 400–550 �m long -------------------------------------------------------------------------- P. majus
10. Flowers mostly closed; pedicels 2–6 mm long; perianth tube 20–28% of the perianth length;
anthers 125–150 �m long ------------------------------------------------------------------------------------------------- P. douglasii
9. Ocreae 3–5 mm long; flowers and achenes 2–3 mm long.
11. Inflorescence dense, cymes overlapping at stem and branch apices; flowers wide-open, with
the tube 10–15% of the perianth length; anthers 325–380 �m long ------------------------ P. gabrielae
11. Inflorescence elongated, spike-like, cymes spaced along stem and branches; flowers closed,
with the tube 25–33% of the perianth length; anthers 100–160 �m long.
12. Tip of mature achene exserted from perianth; lower leaves linear-oblanceolate with
smooth margins ---------------------------------------------------------------------------------------------------- P. engelmannii
12. Tip of mature fruit enclosed in perianth; lower leaves broadly elliptic to ovate, with
margins minutely denticulate-papillose ----------------------------------------------------------------- P. austiniae
1. POLYGONUM TENUE Michx., Fl. Bor.
Amer. 1: 238. 1803. TYPE: CANADA.
‘‘Herbier de l’Amérique septentrionale.
In Canada, at Mona Caesarea ad Snake
Bill,’’ Michaux s.n. (LECTOTYPE, here designated:
P, specimens on left side of
sheet).
Polygonum tenue var. protrusum Fernald, Rhodora
44: 393. 1942. TYPE: United States. Virginia.
Southhampton Co.: Blackwater River, SE of Ivor,
16 Oct 1941, Fernald & Long 13937 (HOLOTYPE:
GH; isotypes: NY, US).
Annual herbs. Stems 5–50 cm long, 4–
angled, green or brownish, erect, simple or
branched, with a few to many branches, upper
edges glabrous, � winged or denticulate-papillose;
papillae on the edges (when
present) conical, 80–120 �m, papillae on
the stem faces spherical, 7–18 �m, located
at the same level with the epidermis cells
(Fig. 1A). Leaves: basal leaves caducous or
persistent at flowering; upper leaves reduced
to scale-like bracts upward; ocreae
6–15 mm, glabrous, free part soon disintegrating
into a few brown fibers; blades narrowly
lanceolate to linear, with 2 deep
pleats parallel to the midvein, 25–40 � 1–
8 mm, margins usually plane, denticulatepapillose,
apex mucronate or cuspidate. Papillae
on leaf margins conic-elongated or
cylindrical, 110–200 �m. Inflorescences
terminal, spike-like, slender and elongated;
cymes 1 or 2(3)-flowered, widely spaced
along stem and branches; bracts shorter to
equaling the flowers they subtend. Flowers
closed; pedicels erect, 1–1.5 mm; perianth