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.
A small genus of trailing annual or perennial herbs with usually angular stems, opposite or verticillate leaves, and solitary brightly coloured pedunculate flowers. Calyx deeply 5-lobed. Corolla rotate or funnel-shaped. Stamens 5, inserted at the base of the corolla; filaments bearded. Capsule globose, dehiscing transversely, many-seeded. The species are found in Europe, Asia, North Africa and South America; we have two indigenous species. A. arvensis, Poor Man's Weather-glass, is a trailing glabrous glandular-dotted annual with bright scarlet flowers which only expand in bright weather; varieties with pink or white or blue flowers are occasionally found. A. tenella, Bog Pimpernel, is a very small slender perennial species with ovate or orbicular leaves and rosy flowers with darker veins. The generic name is the same as applied by the ancients to one of the common species.
1. A. Indica. - This is the common annual species grown in gardens with deep blue flowers. The flowers are larger than those of the wild species, which it very closely resembles in other particulars.
2. A. Monelli. - A perennial species with deep blue flowers, about 6 lines in diameter in the common variety. But there are varieties with larger scarlet, maroon or lilac flowers, supposed to be the result of hybridized seed between this and A. fruticosa, a handsome species with large vermilion flowers, from North Africa. Breweri, Phillipsi, Parksii, and Phoeni-cea are some of these varieties. They are usually treated as annuals.
Hottonia palustris, Featherfoil or Water Violet, is the only other plant of this order we have to mention. It is a native, but by no means common, growing in ponds and sluggish brooks. Leaves submerged, whorled, deeply divided into numerous thread-like segments. Flowers white, pink or lilac, whorled in terminal racemes.