Comparative anatomical studies in five southern African species of Crassula. I. Structure of the stem and the root

Stem and root anatomical studies were carried out on Crassula dependens Bolus, C. inanis Thunb., C. lanceolata Endl., C. natalensis Schonl., and C. peploides Harv., collected from Lesotho and South Africa. In all the taxi the cells of cortex and pith are entirely parenchymatous and relatively large, imparting the fleshy structure to the stems. Individual vascular bundles are not distinguishable, the vascular tissue consisting mostly of scattered tracheary elements, unlignified parenchyma and very small phloem cells. Electron microscopy reveals that sieve elements and companion cells are well-differentiated. The former are irregularly shaped, thick-walled and contain fibrillar P-protein. The red root tips contain anthocyanin. Secondary growth is uncommon in both the roots and stems, and cambial activity produces either a parenchymatous or sclerenchymatous cylinder. Tanniniferous cells are common in the stems but less so in the roots.