3.1 General leaf morphology
Leaf morphology of the Crassula species examined ranged from planar and bifacial (e.g. C. multicava and C. ovata ) to subterete and equifacial (e.g. C. tecta and C. ausensis ) (Figs. 2, 3 ). Furthermore, leaf orientation varied: leaves were patent in C. multicava , C. ovata and C. perforata , erecto-patent in C. sericea , and erecto-patent to erect inC. fragarioides , C. tecta and C. ausensis . In these three last species, only the distal half of the leaves was exposed to the atmosphere, due to the tight arrangement of the leaves. In the two columnar species, C. deceptor and C. plegmatoides , leaves were wide and short and tightly arranged, so that the abaxial side of the leaves was predominantly exposed to the atmosphere.