keys to the vascular plants of east texas - Botanical Research ...

690 IRIDACEAE/IRIS
LOUISIANA IRISES are rhizomatous, have laterally compressed (flat-appearing) leaves and beardless
falls, and are very variable in color. Hybridization, including introgressive hybridization (=
hybridization resulting in movement of genes from one species to another), in LOUISIANA IRISES
has been studied in detail and has been argued to be of long-term evolutionary significance
(e.g., Anderson 1949; Arnold et al. 1990a, 1990b, 1991, 1992; Nason et al. 1992; Arnold 1993; Arnold
& Wesselingh 2000). Pollination in IRISES: each petal-like style branch is opposite one of
the three outer perianth segments (= sepals ) and there is a stamen between it and the sepal. The
sepals typically act as landing platforms for pollinating insects such as bees. On the underside
of each style branch, near the apex, is a little flap of tissue whose upper surface is sticky—this is
the stigma. When an insect (presumably carrying pollen) lands on one of the sepals, it starts to
crawl in between the sepal and the adjacent style branch in search of nectar. In the process, it
makes contact with the sexual organs of the flower. As the pollinator enters the constricted
space, it brushes against the flap of stigmatic tissue which is pulled downward to expose the
sticky stigmatic surface. As a result, pollen on the insect’s body is rubbed off onto the sticky receptive
surface of the stigma. In addition, pollen from the adjacent anther is deposited onto the
insect’s body during its foraging for nectar. When the pollinating insect exits the reproductive
area of the flower (carrying the flower’s pollen), the little flap of stigmatic tissue is moved back
upward, which is thought to prevent self-pollination (Faegri & van der Pijl 1979; Mabberley
1997). IRISES are also known to produce self-incompatible pollen, which promotes cross-pollination
and prevents self-fertilization. “Asexual reproduction in many Iris species may be more
important than sexual reproduction in their persistence, and many hybrid clones may persist
for decades in sites no longer cultivated” (Henderson 2002). The common name FLAG is derived
from the Middle English flakken, to flutter, in reference to fluttering in the wind (Durant 1976).
(Named after Iris, Greek goddess of the rainbow, from the varied flower colors)
REFERENCES: Dykes 1913; Anderson 1936, 1949; Foster 1937; Riley 1938; Arnold et al. 1990a,
1990b, 1991, 1992, 1993; Mathew 1990; Henderson 1992, 1994, 2002; Nason et al. 1992; Arnold
1993, 1994; Cruzan et al. 1993; Species Group of the British Iris Society 1997; Arnold &
Wesselingh 2000; Caillet et al. 2000.
1. Leaves nearly cylindrical, channeled on upper surface; plant with a bulb ______________________ I. xiphium
1. Leaves laterally compressed, appearing � flat, the two surfaces identical; plant with a thick rhizome.
2. Perianth dark red to reddish brown, coppery brown, orange, or yellow (without blue or purple
coloration when fresh, but sometimes drying with purple areas); sepals (= falls) without a
beard (= hairy patch).
3. Perianth bright yellow to golden yellow; fruits 3-angled; petals (= standards) much
shorter than sepals ________________________________________________________ I. pseudacorus
3. Perianth dark red to reddish brown, coppery brown, or orange; fruits 6 angled; petals
nearly as long as sepals (but narrower) _______________________________________________ I. fulva
2. Perianth bluish, purplish, or white (or variously colored in cultivated forms); sepals without an
obvious beard OR with a beard of multicellular hairs.
4. Sepals with a beard of multicellular hairs; petals (= standards) 30–60 mm wide; introduced
species.
5. Spathes entirely scarious (= dry, papery, and translucent or transparent) and silvery white
at flowering time, 20–35 mm long; perianth tube 8–13 mm long ______________________ I. pallida
5. Spathes scarious in the upper half, the lower half greenish, sometimes with purplish
tinge at base at flowering time, 35–55 mm long; perianth tube 17–25 mm long _______ I. germanica
4. Sepals without an obvious beard (but can have very short pubescence); petals 10–30 mm
wide; native species.
6. Cauline leaf immediately subtending spathes usually shorter than to slightly longer than
the spathes or absent; stems nearly as long as or longer than the basal leaves, not zigzag;
ovaries and fruits 3-angled ________________________________________________ I. virginica