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.
The larger kind, V. major, with large blue flowers, and the lesser one, V. minor, similar but smaller in all its parts, are well-known trailing evergreen shrubs with ovate glossy leaves. There is a white-flowered, and double blue-flowered form of V. minor, and one with silvery variegated leaves. V. rosea is a pretty greenhouse plant, with rose flowers, from Madagascar.