This section is from the book "Wayside And Woodland Blossoms", by Edward Step. Also available from Amazon: Wayside And Woodland Blossoms: A Guide To British Wild-Flowers.
Should any reader who has not previously made a study of botany, but who has followed us thus far, be asked to name the order to which the Scabious belongs, he would almost certainly say the Compositae. He would be wrong, but almost right. Scabious is certainly a Composite flower, though not one of the Compositae; it is, instead, included in the order Dipsaceae. We have already made the acquaintance of so many composite flowers that our readers may be presumed to be fairly familiar with their general structure. It will be remembered, then, that the anthers of Composites are all joined together to form a tube: in Dipsaceae they are free. Again, the calyx in Compositae is reduced to a series of hairs (pappus), whilst in Dipsaceae there is a distinct tubular calyx invested in a separate involucel (or little involucre) of tiny bracts, quite independent of the common involucre that invests the whole head of florets.
I. The Field Scabious (.S. arvensis), is a perennial with a stout rootstock, and a hairy stem. The leaves vary considerably in different specimens, but usually those from the root are entire, of an oblong lance-shape, with toothed margins. The stem leaves are lobed, sometimes almost pinnate. The flower-heads are borne on a long stout stalk, and consist of about fifty florets, increasing in size from the centre to the outer margin, and of a pale blue or lilac colour, the central ones more inclined to red; anthers yellow. Involucral bracts broad and leaf-like, in two rows. Dry fields and downs. June to September.
II. Devil's-bit Scabious (S. succisa). Rootstock short, coming to an abrupt conclusion, as though bitten off. Culpepper accounts for this and the name by saying: "This root was longer, until the Devil (as the friars say), bit away the rest from spite, envying its usefulness to mankind; for sure he was not troubled with any disease for which it is proper." Leaves all entire. Involucral bracts lance-shaped, shorter than the corollas, in two or three rows. Anthers reddish-brown. Florets nearly equal in size. Flowers purplish-blue, sometimes white. July to October, in meadows and pastures.
III. Small Scabious (S. columbaria). Rootstock thick and woody. Root leaves entire, narrow; stem leaves deeply cut, almost pinnate. Involucral bracts longer than the corollas, in one row. Corollas five-lobed (in the other species four-lobed), the outer row considerably larger than the inner ones, and of irregular form. Anthers yellow, corollas purplish-blue. July to September, in pastures and wastes.
The name is derived from the Latin, scabies, the itch, it being formerly used in curing this and other cutaneous disorders.