Some more pictures from the Crassula family.
1, 2, 3 Cotyledon orbiculata var. orbiculata: a perfect example of a Very Variable Variety.
4 Cotyledon tomentosa var. tomentosa
5, 6, 7 Kalanchoe thyrsiflora
The whole plant, especially the inflorescence, often exudes a sticky substance. This does not only trap a lot of dust and sand particles, but also many insects which might otherwise have damaged the plant.