This section is from the book "Commercial Gardening Vol2", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
This is the well-known "Fishbone Thistle" of South Europe. It is an ornamental plant, 2-3 ft. high, with deep green spiny fishbone-like leaves, distinctly veined with white. The flowers are pale purple, but the plants are valued for their ornamental appearance, and are frequently used for bedding purposes. C. diacantha, from Syria, is similar, but is easily distinguished by the silvery veins and double ivory-white spines of the leaves. Both kinds are raised from seed sown in gentle heat, the young plants being pricked out in due course, and placed in 3½-in. or 5-in. pots later on for sale, which, however, is limited.