Jones L. A., Anatomical adaptations of four Crassula species to water availability, Bioscience Horizons, 2011, 4(1):13-22, doi: 10.1093/biohorizons/hzr002
The comparison of four species includes leaf and stem sections, cuticle measurements and densities of stomata and hydathodes. Two succulence indices rank the species differently depending on whether water content is related to leaf area or organic matter mass. Material came from cuttings of four stock plants maintained in a greenhouse.