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

2 BRITTONIA
[VOL. 57
DAO, DC, DS, GH, F, JEPS, LL, MT,
MTMG, NY, OAC, POM, QFA, RSA,
SASK, TEX, UBC, UC, US, and USAS.
Mature plants with leaves, flowers, and
achenes are necessary for accurate determinations.
Plants parasitized by homopteran
insects are atypical. Their internodes are
shortened, cymes have numerous flowers,
and inflorescences are denser; flowers are
brownish, sterile, and pedicels may be erect
even in taxa in which they are normally reflexed.
Papillae are easily observed on
young stems or toward apices of mature
stems and branches, at magnifications higher
than 50�. Measurements of leaves and
ocreae were made at the middle of the main
stem. The state characters, ‘‘flowers
closed,’’ ‘‘flowers semiopen,’’ and ‘‘flowers
wide-open’’ were noted on herbarium specimens.
Description of perianth refers to the
fruiting perianth, which was measured from
the joint with the pedicel. Morphology of
pedicels was noted in fruit. Measurements
of dry anthers were obtained from SEM
pictures (see below).
MICROMORPHOLOGY
Samples (Appendix 1) were collected
from typical herbarium specimens within
the holdings of CAS, DS, GH, JEPS, NY,
RSA, UC, and USAS. Samples were coated
with 30 nm gold using an Emitech
K550� Sputter Coater and examined with
a Hitachi S-570 at 15 KV. Micromorphology
of the following organs or plant parts
was examined: mature stems and leaves,
fruiting perianth, and pollen. Surface pattern
of perianth was studied on the borders
of the outer perianth lobes. Standard terminology
for cell types and surface sculpturing
patterns follows Ronse Decraene
and Akeroyd (1988), Barthlott et al.
(1998), and Hong et al. (1998). Pollen terminology
follows Hoen (1999). Description
of achene morphology and micromorphology
follows the terminology developed
by Wolf and McNeill (1986) and
Ronse Decraene et al. (2000).
STEMS
Results
Stems are 4-angled, with smooth (Fig.
1A) or minutely and irregularly ribbed fac-
es (Fig. 1C, D, F). Epidermis cells are rectangular
or elongated, with epicuticular wax
consisting of longitudinal rodlets (Fig. 1C).
Stomata are frequent, mostly anisocytic
(rarely a few may be anomocytic). Presence
of papillae is a distinctive feature observed
in many taxa. Papillae may be distributed
on the stem angles or on the ribs and between
these (Fig. 1C, D, F). They may be
patent or more or less retrorse. Papillae
shape varies from � spherical, 7–18 �m,
located at the same level with the epidermis
cells (Fig. 1A), conical with a swollen base,
40–60 �m (Fig. 1B), to conical-elongated
or cylindrical, 100–200 �m long, approaching
hairs (Fig. 1C, D). Epicuticular wax of
papillae is organized as parallel rodlets
(Fig. 1B).
LEAVES AND OCREAE
Leaves are obviously jointed to ocreae,
which may be short, funnelform 2–5 mm,
or longer, 5–12 mm, with the free part becoming
lacerate or disintegrating into a few
fibers. Petioles are very short or absent.
Blades are variably shaped, linear to round,
and 1-veined. Leaf blade epidermis cells are
irregularly shaped or elongated, with more
or less undulate anticlinal walls. Stomata
are usually present on both epidermis, and
they are mostly anisocytic (rarely a few
may be anomocytic). Margins of the leaves
are often revolute (Fig. 2A), or sometimes
plane. In P. utahense, the revolute margins
join together on the abaxial side of the
blade (Fig. 2B). Conical or conical-elongate
papillae, similar to those present on the
stems, may occur on the ocreae and lamina
margins in many taxa (Fig. 1F, 2C, D).
Presence of papillae on the rest of lamina
has been documented only in P. utahense
(Fig. 2B, F) and sometimes in P. spergulariiforme
(Fig. 2E). Epicuticular wax is organized
as longitudinal rodlets or threads
(Fig. 2E); only in P. utahense do the rodlets
form a reticulate pattern (Fig. 2F).
PERIANTH
The perianth consists of two outer tepals,
one intermediate (transitional), and two inner
tepals fused for 8–40% of their length.
The outer and the intermediate perianth