IRIS. In botany, the iris plant belongs to the family Iridaceae of the class Monocotyledons ; it is characterized by a petaloid six-parted perianth, an inferior ovary and only three stamens (the outer series), being thus distinguished from the Amaryllidaceae family, which has six stamens. They are handsome showy-flowered plants, the Greek name having been applied on account of the hues of the flowers. The genus contains about 20o species widely distributed throughout the north temperate zone. Two of the species are British. I. Pseudacorus, the yellow flag or iris, is com mon in Britain on river-banks, and in marshes and ditches. It is called the "water-flag" or "bastard floure de-luce" by Gerard ; its flowers appear in June and July, and are of a bright golden-yellow colour. The other British species, I. foetidissima, the fetid iris, gladdon or roast-beef plant, the Xyris or stinking gladdon of Gerard, is a native of England south of Durham, and also of Ire land, southern Europe and North Africa.
In North America there are about 20 native species, found chiefly in the eastern United States ; among the best known are the blue flag (I. versicolor) which grows in wet places from New foundland to Manitoba and southward to Florida and Arkansas, and the western blue flag (I. missouriensis), native to wet soils from North Dakota and New Mexico westward to California and British Columbia.
Iris florentina, with white or pale-blue flowers, is a native of the south of Europe, and is the source of the violet-scented orris root used in perfumery. Iris germanica of central Europe, "the most common purple Fleur de Luce" of Ray, is the large common blue iris of gardens, the bearded iris or fleur de Luce and probably the Illyrian iris of the ancients. The garden plants known as the
Spanish iris and the English iris are both of Spanish origin, and have very showy flowers. Along with some other species, as I. reticulate and I. persica, both of which are fragrant, they are great favourites with florists. All these just mentioned differ from those formerly named in the nature of the underground stem, which forms a bulb and not a strict creeping rhizome as in I. Pseudacorus, germanica, florentina, etc.
The iris flower is of special interest as an example of the relation between the shape of the flower and the position of the pollen receiving and stigmatic surfaces on the one hand and the visits of insects on the other. The large outer petals form a landing-stage for a flying insect which in probing the perianth-tube for honey will first come in contact with the stigmatic surface which is borne on the outer face of a shelf-like transverse projection on the under side of the petaloid style arm. The anther, which opens towards the outside, is sheltered beneath the over-arching style arm below the stigma, so that the insect comes in contact with its pollen covered surface only after passing the stigma, while in backing out of the flower it will come in contact only with the non-recep tive lower face of the stigma. Thus an insect bearing pollen from one flower will in entering a second deposit the pollen on the stigma, while in backing out of a flower the pollen which it bears will not be rubbed off on the stigma of the same flower.