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.
Annual or perennial herbs, differing from the last genus in having the calyx constricted at the top and not membranaceous between the nerves, and from Silene in having only two styles, and especially in the obscure nervation of the calyx. There are about thirty species, chiefly from southern Europe and extra-tropical Asia. The name is from the Latin sapo, soap, from the properties of S. officinalis.
1. S. officinalis. Soapwort. - An erect glabrous rather stout perennial plant 2 to 3 feet high. Leaves oblong-lanceolate, about 3 inches long, 3-ribbed. Flower 1 inch across, pink or white, double or single, produced in terminal clustered cymes. This is found in some parts of England, but is not truly indigenous. There is a variety called hybrida having a monopetalous corolla.
2. 8. ocymoldes. - A dwarf densely-branched procumbent perennial species with ovate-lanceolate leaves and rosy purple or pink flowers. A very desirable little plant, producing its flowers in abundance nearly all the Summer. A native of Europe.
3. S. Caldbrica. - This is of annual duration and one of the handsomest of that class of plants. It does not exceed a foot in height and its rosy-pink flowers though small are so numerous as to be highly effective. There is also a white-flowered variety. South of Europe.