Aspects of Sieve Element Ontogeny and Structure in Smilax rotundifolia

The sieve elements of Smilax rotundifolia are long slender cells with sieve plates which range from transverse and simple to very oblique and much compounded. At maturity the enucleate sieve element is lined with a thin layer of cytoplasm which incloses a large central cavity traversed by numerous strands. The latter are apparently derived from the slime bodies of immature elements. Many sieve elements remain functional for 2 years or more. During cessation of function of sieve elements, their associated companion cells form tyloses or tylosis-like structures and subsequently become sclerified.