In this article we will discuss about:- 1. General Features of the Iridaceae 2. Floral Range in the Iridaceae 3. Divisions 4. Position and Affinity 5. Number and Distribution 6. Commonly Occurring Plants 7. Economic Aspects.
General Features of the Iridaceae:
Habit – Perennial herbs with a bulb, corm or rhizome.
Stem – Solitary, several or none.
Leaves – Radical, equitant, linear or ensiform.
Inflorescence – Panicle or raceme or solitary.
Flowers – Showy, bisexual, regular or irregular, epigynous.
Perianth – Segments 6, in 2 whorls, petaloid.
Androecium – Stamens 3, alternate with petals’, anther 2-celled, extrorse.
Gynoecium – Carpel 1; ovary inferior, trilocular with axile placentation or unilocular with parietal placentation.
Fruit – Loculicidal capsule.
Seeds – Angular or roundish by compression; embryo small; endosperm fleshy or hard.
Floral Range in the Iridaceae:
The flowers are solitary in Crocus and Romulea. Both regular and irregular flowers are found in Gladiolus. The inner series of perianth is usually smaller than the outer. The stamens are united into a tube in Sisyrinchium grandiflorum. The ovary is unilocular with a parietal placentation in Hermodactylon.
The style-arms are short and bifid in Freesia, Watsonia and related genera; simple (undivided) in Gladiolus, Sisyrinchium, etc. simple and flattened or very variously divided in Crocus and large, broad and petaloid in Iris and allied genera.
Divisions of the Iridaceae:
The Iridaceae is divided into three subfamilies:
Subfamily I. Crocoideae:
Leaves linear or filiform in several rows. Spathe 1-flowered. Flowers regular. Perianth whorls subequal. Examples- Crocus and Romulea.
Subfamily II. Iridoideae:
Leaves equitant, in 2 rows. Spathe 2 to several-flowered. Flowers regular. Perianth whorls unequal. Examples- Belamcanda, Iris, Sisyrinchium, etc.
Subfamily III. Ixioideae:
Leaves equitant, in 2 rows. Spathe 1-flowered. Flowers medianly zygomorphic. Examples- Gladiolus, Ixia, etc.
Position and Affinity of the Iridaceae:
The Iridaceae is generally included in the Liliiflorae (Liliales). However, Hutchinson placed the family in an order by itself (Iridaies). Takhtajan’s Iridaies included not only the Iridaceae but also the Geosiridaceae, Burmanniaceae and Corsiaceae.
The Iridaceae, while resembling the Amaryllidaceae in the inferior ovary and that family and the Liliaceae in the germination of seeds, is distinguished from other families of the Liliales by the presence of a single whorl of stamens. Moreover, the pollen grains of the Iridaceae and Amaryllidaceae are similar.
Like the arborescent Liliaceae and Amaryllidaceae, secondary growth takes place by cambial activity in some members of the Iridaceae (Aristea Klattia, Witsenia). The Iridaceae is related to the Haemodoraceae in which the outer whorl of stamens is suppressed instead of the inner whorl.
It has been assumed that the Iridaceae originated from the liliiflorean stock or directly from the Amaryllidaceae by way of reduction in the inner whorl of stamens.
Number and Distribution of the Iridaceae:
A family of about 70 genera with 1,800 species, the Iridaceae is distributed over much of the earth except the coldest regions. The chief centres of distribution are South Africa and tropical America.
Commonly Occurring Plants of the Iridaceae:
Belamcanda chinensis (L.) DC, Cipura paludosa Aubl. and Iris clarkei Bak. are garden plants.
Economic Aspects of the Iridaceae:
The Iridaceae is of considerable economic importance for ornamentals, e.g., Antholyza, Belamcanda, Crocus, Crocosmia, Eustylis, Freesia, Gladiolus, Iris, Ixia, Moraea, Nemostylis, Neomarica, Romulea, Sparaxis, Sisyrinchium and Tigridia. ‘Saffron’, a yellow dye, is obtained from the dried stigmas of Crocus sativus. The dried rhizomes of Iris florentina, L. germanica var. germanica and I. pallida constitute ‘orris root’, a violet perfume. The rhizome of I. foetidissima serves as a specific for hysteria.
No comments yet.