This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
Annual or perennial herbs, distinguished by the 4 nuts being furnished with a membranous inflexed wing or border which renders them cup-shaped. There are several species from Southern Europe and Western Asia. The name is from the navel, and form or shape, the resemblance of the nuts.
1. 0. verna. Venus's Navel wort. - A handsome and early-flowering herbaceous perennial with creeping branches and ascending flowering shoots about 6 inches high. Lower leaves cordate, on long slender petioles, glabrescent, upper narrower. Flowers blue, about half an inch in diameter, in loose racemes, appearing in March and April. South of Europe.
2. 0. linifolia. - A glaucous annual about a foot high with narrow leaves and long racemes of white flowers tinged with blue. A native of Portugal.
Gynoglossun is a neighbouring genus whose species have ample foliage, blue, purple or reddish flowers, followed by large shortly stalked prickly nuts. G. officinale has dull red flowers, and G. montanum bluish flowers; neither is very common in Britain.
Lindelofia spectdbilis, syn. Cynoglossum longiflorum, is a neat-growing perennial about a foot high with oblong leaves and racemes of showy blue flowers. It is from North India, and flowers towards the end of Spring.