This section is from the book "British Wild Flowers - In Their Natural Haunts Vol2-4", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
This choice wild flower has much the same range as other Liliaceous flowers, the North Temperate Zone of Europe (except Greece and Turkey), and West Asia, and is not known before the present day. In Great Britain it is found in the Peninsula province only in N. Somerset; in the Channel province only in N. Wilts, Hants, in the Thames province, not in E. Kent; Anglia, not in W. Norfolk, Hunts, Northants; in the Severn province only in W. Gloucs, Worcester, Warwick, Stafford. Watson thinks it is not indigenous in E, Cornwall, S. Devon, Dorset, W. Sussex, Salop, Leicester, N.E. Yorks, Westmorland, Cumberland, and Ayr, and perhaps not even in all of the foregoing. But in Leicestershire it is truly native, growing in the same habitat as in the Thames valley. But it is rare from Norfolk and Stafford to Somerset and Hants.
This is by no means a common plant, and the only spots in which it is likely to occur are flat meadows on either side of rivers, especially in wide open valleys where recent alluvium occurs. It is a graceful flower with a bulbous rhizome and fibrous roots, growing in scattered clumps here and there. The leaves (4-5) are alternate, channelled, linear lance-shaped, stalkless, not sheathed. The stem is erect, simple, bluish-green, and rounded.
The flower is chequered, of a purple colour, with white and darker patterns interwoven, or pure white. In shape the flower is like a snake's head, or a dice-box, hence the English and first Latin names. I he flowering stems bear single flowers, which are drooping, and there is no calyx. The petals or petaloid sepals are 6 in number, swollen below. The 6 anthers are yellow, the stamens being inserted below the ovary.
The Fritillary is about 1 ft. high. One may look for the flowers in March, April, and May. Snake's-head Fritillary is a perennial bulbous plant, propagated by offsets, suited to growing under trees.