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.
Climbing evergreen shrubs with simple leaves. Flower-umbels paniculate. Petals valvate, with an equal number of stamens. Seeds with ruminated albumen. The derivation of the name is obscure, but supposed to be from the Celtic hedra, a cord, in allusion to the stems. There is an Australian species with pinnate leaves, and all the other forms are referred to one species by some botanists, and by others they are grouped under several different names. The extreme varieties are very distinct and readily recognised, but there are some intermediate forms which are not so easily disposed of. The Ivies are found throughout the north temperate and warm regions of the Old World, and some of the forms are local, which has led to their receiving names indicative of the countries they inhabit, whilst others have been less appropriately named. Without committing ourselves on the species question, we will enumerate a few of the most distinct forms. It should be remembered that the leaves on young plants and on flowering branches are often very different from the bulk. Ivies rarely flower in the creeping form, or when climbing until they have reached the summit of the support, where they assume a different closer stouter growth and produce flowers.
1. H. Helix, Common Ivy. - The varieties of this are numerous and handsome. Flowering specimens, it is said, may be distinguished by the pedicels and calyx being clothed with 6- to 8-rayed stellate hairs. But the names are almost sufficiently descriptive of the peculiarities of the garden forms, as: pedata, palmata, rugosa, lucida, sagittaefolia, minor marmo-rata, aurea marginata, argentea marginata, etc. There are also green and variegated arborescent forms, and others with white, yellow, or black berries.
2. H. Canariensis, or Hibernica. Usually known in gardens as the Irish Ivy. - Stellate hairs of the inflorescence with 13 to 15 rays. Algertensis is one of the best green-leaved varieties referred here. Though the variegations are not so numerous and varied, there are some very desirable, generally of more robust and vigorous growth than in No. 1 : pallida, maculata, argenteo-marginata, Gavendishii, etc.; arborescens and cordifolia are 'Tree Ivies.'
3. H. Rozgneriana or Colchica. Giant Ivy. - Inflorescence furnished with 2-lobed scales, each lobe again divided into 7 to 10 teeth. The leaves of this form are very large, thick and leathery. There is a variety, arborea, both green and variegated.