This section is from the book "Commercial Gardening Vol4", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
Apart from the lovely greenhouse plant C. fragrans (see Vol. II, p. 165), there are several ornamental shrubs grown in large numbers, many of them being easily raised from seeds, while the choicer or rarer kinds are increased by cuttings, layers, or grafting. Amongst the best-known kinds are albus, 6-10 ft., white; Ardoini, a dwarf trailing shrub, 1 ft., with yellow flowers; biflorus, 3 ft., bright yellow; kewensis (a hybrid between albus and Ardoini), with creamy - yellow flowers; nigricans, 3-6 ft., yellow; proscox, 8-10 ft. (a hybrid between purgans and albus), sulphur yellow, and one of the first to flower; purpureus, a trailing shrub with purple flowers. There is a white-flowered variety, albus, and a yellow one called ratisbonensis; Scoparius is the common British Broom, with twiggy branches and bright-yellow flowers from April to July. There are several varieties in which white and pale-yellow flowers appear, and also double ones; Andreanus (often called Genista) has yellow flowers blotched with rich brownish purple. It is a favourite pot plant for early forcing.