mix a mild fungicide or weak strength horticultural sulfur into the plant's water to prevent rotting. Lithops are sensitive to watering during hot weather, which can cause the plants to rot; in habitat the plants are often dormant when the temperatures are high, doing most of their growing during the cool months of the year. Low light levels will make the plants highly susceptible to rotting and fungal infection. In the United Kingdom the following species have gained the Royal Horticultural Society’s Award of Garden Merit:- Lithops karasmontana Lithops olivacea Lithops pseudotruncatella Lithops salicola Lithops schwantesii Propagation Propagation of Lithops is by seed or cuttings. Cuttings can only be used to produce new plants after a plant has naturally divided to form multiple heads, so most propagation is by seed. Lithops can readily be pollinated by hand if two separate clones of a species flower at the same time, and seed will be ripe about 9 months later. Seed is easy to germinate, but the seedlings are small and vulnerable for the first year or two, and will not flower until at least two or three years old. History The first scientific description of Lithops was made by botanist and artist William John Burchell, explorer of South Africa, although he called it Mesembryanthemum turbiniforme. In 1811, Burchell discovered a specimen when picking up a "curiously shaped pebble" from the ground. Unfortunately the documented physical description was not detailed enough to be sure which Lithops he had discovered and the name Lithops turbiniformis is no longer used, although for many years it was applied to what is now known as Lithops hookeri. Several more Lithops were published as Mesembryanthemum species until in 1922 N E Brown started to split up the overly large genus on the basis of the capsules. The genus Lithops was created and dozens more species were published in the following decades. Brown, Gustav Schwantes, Kurt Dinter, Gert Nel, and Louisa Bolus continued to document Lithops from across southern Africa, but there was little consensus on the relationships between them, or even which populations should be grouped as species. As recently as the 1950s, the genus remained rather unknown in cultivation and was not well understood taxonomically. In the 1950s, Desmond and Naureen Cole began to study Lithops. Together, the couple visited nearly all natural habitats of the different lithops populations and collected samples from approximately 400. They