Iris flowers helped launch a classic statistics experiment in 1936
Ronald Fisher's 1936 paper on using multiple measurements in taxonomy relied on three kinds of iris. The resulting iris flower data set became a standard example of linear discriminant analysis. Gardeners, meanwhile, still chase something breeders have never achieved: a bearded iris that is truly red.
Iris is a genus of about 320 accepted species, most of them in temperate parts of Europe, Asia and North America. Many prefer dry, semi-desert or cold rocky mountain ground, though others live in meadows, woods, bogs and along rivers. The name is the Greek for rainbow, and some writers link it to the enormous range of flower colours. Some species are called flags, and bulbous junos form their own subgenus.
The flower is a piece of pollination engineering. Three outer sepals, called falls, spread or droop, while three petals, the standards, stand upright. In bearded irises a strip of fuzzy hairs on each fall gives visiting insects a landing strip and points them toward the nectar. On the way in, the insect brushes against the stigma surface and then against pollen, so it carries pollen from one flower to the next. The fruit is a capsule that splits in three to release its seeds.
Irises are prone to crossing. The very idea of introgressive hybridisation, in which hybrids breed back into a parent species, was first coined to describe what happens in this genus. Taxonomists since W. R. Dykes in 1913 have divided it into groups; modern schemes recognise six subgenera, five confined to the Old World.
Few garden plants are so collected. The American Iris Society registers more than 30,000 cultivar names, New Jersey's Presby Memorial Iris Gardens hold over 10,000 plants, and Florence's Giardino dell'Iris hosts a breeding competition each year. Modern bearded irises have been bred to about twice their historical size. The common so-called German iris of European gardens is actually a sterile hybrid. The Copper iris, I. fulva, has fairly pure red flowers, but transferring that colour into bearded varieties has so far failed.
Source: Iris (plant)
