Rock gardeners are famous for their bun fixations: more than one casual visitor at a rock garden meeting has been put off by people constantly commenting on one another's buns, extolling buns and saying how much they love to pat buns. Of course, they are referring to the cushiony form of plants in extreme environments. Above you have Erinacea pungens (top) and Acantholimon ulicinum (bottom), two cushion forming buns you shan't want to pat: the picture was taken a week or so ago in the Rock Alpine Garden at DBG: a bunnery.
Many succulents form buns, especially in our climate. Above we have various clones of Stomatium mustellinum, a wonderful night blooming succulent from the Drakensberg. I am fascinated how different the coloration is between one plant and another: all from the same wild pinch of seed.