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.
Erect perennial herbs with tough fibrous bark. Leaves opposite, mucronate. Flowers cymose, on axillary or terminal peduncles. Corolla campanulate, bearing five triangular appendages at the mouth of the tube. Fruit of two slender follicles; seeds plumose at one end. There are three North American and one South European species. The name is a compound of from, and a dog, supposed to be poisonous to dogs, whence the English name Dogbane.
1. A. androsaemifolium. Fly-trap. - A branching herb from 1 to 2 feet high with ovate glabrous petiolate leaves and small pale red flowers in loose cymes. Corolla-tube much longer than the calyx-lobes. An interesting and curious plant remarkable for the irritability of the glutinous throat-appendages, which collapse upon intruding insects and retain them prisoners. A native of North America, flowering towards the end of Summer.
A. cannabinum, Indian Hemp, is a variable species having several synonyms. The flowers are greenish white, and the corolla-tube does not exceed the calyx-lobes. A. Venetum is the European species.
The Oleander, Nerium Oleander (fig. 168), is really a greenhouse plant with us, though it will exist in the open air in the South-west of England if protected in Winter. It may be well to mention that this plant, so commonly seen in windows, is excessively poisonous. There are many handsome double-flowered varieties. Parechites Thunbergii, better known in gardens under the name of Rhynchospermum jasminoides, is very commonly grown in conservatories for its pure white deliciously scented flowers, and bears the popular name of Cape Jessamine, but it is a native of Japan and China. It will succeed against a south wall with slight protection in severe weather, though it does not bloom freely without the warmth of a greenhouse.
Fig. 168. Nerium Oleander floribus plenis.