Succulent collectors, especially those in southern California, will be familiar with C. tetragona through its subspecies robusta.  The latter is commonly grown in succulent gardens as it is easily propagated and shared with friends.  Many may be unaware of its name but will readily recognize its distinctive silhouette of four-ranked leaves atop bare, 1 m tall stems.  Subspecies connivens has a similar four-ranked symmetry, but in miniature, and with occasional shearing and shaping it makes a superb succulent bonsai with a thickened trunk covered with peeling parchment-like bark.  It occurs on dry slopes in both the W. and N. Cape.  Unfortunately, ours came to us without more specific data.  Rooted cuts of HBG 95215.  $6.