Vascular anatomy in vegetative shoots of Ripogonum scandens Forst. (Smilacaceae)

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Abstract
Aspects of the vascular anatomy in the vegetative shoots of Ripogonum scandens Forst., a lianoid plant with mainly decussate phyllotaxis are described. The vascular system can be related entirely to leaf traces and, in the aerial shoots, is not complicated by a nodal plexus, “reseau radicifère”, or cortical system. The two trace complements departing at each node are intimately related; opposing L1, L2, and L4 arise, respectively, from common strands and the common strand of L1 continues as the median of the next leaf above. All traces are several internodes long in cataphyll-bearing shoots but complete elucidation of their length was prevented by internodal elongation. The traces appear to develop acropetally through several plastochrones. Many traces pass to axillary buds. They arise from, or near, departing leaf traces and form a peripheral band before entering the bud. In a mature branch the maximum number of traces is established in the lowermost one or two internodes. The number decreases distally although a zone with a steady state is generally encountered. These findings are discussed in relation to other monocotyledons.