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Published In: Species Plantarum 1: 38. 1753. (1 May 1753) (Sp. Pl.) Name publication detailView in BotanicusView in Biodiversity Heritage Library

Project Name Data (Last Modified On 7/9/2009)
Acceptance : Accepted
Project Data     (Last Modified On 7/22/2009)


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2. Iris L. (iris, flag, fleur-de-lys)

Plants with rhizomes. Aerial stems sometimes very short, mostly erect or ascending (decumbent in I. brevicaulis), circular in cross-section. Leaves appearing 2-ranked or basal, flat. Inflorescences unbranched or sometimes few-branched, of 1 to several clusters of flowers subtended by reduced, leaflike bracts, the clusters with 1–3 flowers enclosed by a pair of spathelike, herbaceous or papery bracts. Flowers with stalks 3–80 mm long. Perianth with a well-developed tube at the base, the sepals and petals much different in size and position, the 3 sepals spreading, reflexed, or arching downward and mostly obovate to spathulate, the 3 petals erect to spreading, linear to obovate. Stamens usually not fused basally. Styles with the 3 style branches enlarged and petaloid, positioned over the sepals and concealing the stamens, 2-lobed at the tips, the stigmatic area at the base of these lobes and covered by a flap of tissue. Capsules oblong, nearly circular in cross-section to bluntly 3- or 6-angled. Seeds flattened, with a fleshy to gelatinous aril (except in our crested species). Two hundred to 300 species, North America, Europe, Asia, northern Africa, cultivated worldwide.

The genus Iris is far more variable morphologically than is accounted for in the preceding description. It also has a long history of cultivation for ornamental, cosmetic, and medicinal purposes that potentially dates to ancient Egyptian times (Mabberley, 1987). Essential oils present in the rhizomes of some of the bearded species have a strong smell of violets (tincture of orrisroot) and are still used commercially to simulate the smell of violets in some perfumes and cosmetic powders. Mathew (1981) presented the most detailed summary of the numerous cultivated species, their characteristics, and their origins. In conjunction with plant breeding and domestication, a specialized terminology has evolved for the perianth that is variously used in much of the literature. The sepals are referred to as falls, with the narrow, stalklike bases called hafts. The sepals may be variously flat, ridged, crested, or bearded. The petals are referred to as standards, and their narrowed bases are usually called claws. Regardless of relative position, it is the sepals that always have the stamens and petaloid style branches overlaying them.


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1 Sepals with a conspicuous beard of long, coarse hairs extending in a line from the narrow base onto the lower half of the broader, apical portion (2)
+ Sepals not bearded, sometimes inconspicuously pubescent with unicellular hairs, ridged longitudinally, or with a fringed, petaloid crest (4)
2 (1) Aerial stems nearly absent, the entire plants less than 25 cm tall (including the leaves) 8 Iris pumila
+ Aerial stems well developed, the plants 40–100 cm tall (including the leaves) (3)
3 (2) Spathelike bracts surrounding the flower clusters green and herbaceous, though often with broad, white to light brown, papery margins 4 Iris germanica
+ Spathelike bracts surrounding the flower clusters grayish white and papery throughout 6 Iris pallida
4 (1) Aerial stems nearly absent, the entire plants less than 30 cm tall (including the leaves) (5)
+ Aerial stems well developed, the plants 30–100 cm tall (including the leaves) (6)
5 (4) Sepals with a conspicuous, fringed, petaloid crest 2 Iris cristata
+ Sepals with an inconspicuous, longitudinal band of minute, papillose hairs...9. I. VERNA (4)
6 (4) Perianth yellow, orange, copper-colored, or reddish brown, lacking blue coloration when fresh (sometimes drying with purple areas) (7)
+ Perianth white, lavender, purple, or blue, sometimes patterned with areas of brown, yellow, and/or green (8)
7 (6) Perianth bright yellow; petals much shorter than the sepals; fruits 3-angled 7 Iris pseudacorus
+ Perianth orange, copper-colored, or reddish brown; petals about as long as the sepals; fruits 6-angled 3 Iris fulva
8 (6) Perianth white, except for a yellow area in the middle of each sepal; fruits 3-angled, with a pair of ribs at each angle 5 Iris orientalis
+ Perianth some shade of lavender, purple, or blue, sometimes patterned with areas of brown, yellow, and/or green, or if rarely all white, then the ovaries and fruits 3- or 6-angled, with a single rib at each angle (9)
9 (8) Aerial stems 10–35 cm long, much shorter than the leaves, decumbent, the flowers thus appearing nearly basal and hidden among the leaves; fruits 6-angled 1 Iris brevicaulis
+ Aerial stems 35–100 cm long, longer than to about as long as the leaves, erect, the flowers thus appearing well elevated from the base of the plant; fruits 3-angled 10 Iris virginica
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