A DEVELOPMENTAL STUDY OF EXTRAFLORAL NECTARIES IN SLIPPER SPURGE (PEDILANTHUS TITHYMALOIDES, EUPHORBIACEAE)'

Slipper spurge (Pedilanthus tithymaloides) bears one or two stalked extrafloral nectaries on either side of the leaf base and one at the leaf tip. The mature nectary is differentiated into multicellular zones: head, neck, and stipe. The nectary arises as a small group of meristematic cells with densely staining cytoplasm and nuclei. The columnar secretory cells show changes in their chemical nature at different developmental stages of the nectary. There is a basipetal sequence in the development and decay of the tissues in the nectary. Decay of the nectary begins at the head, abscission occurs at the line between stipe and neck regions, and the scars of the fallen nectaries are left when the stipe cells also collapse. METCALFE AND CHALK (1950) have described extrafloral nectaries in 23 families of dicotyledonous plants. Such nectaries occur on stipules; on abaxial and adaxial surfaces of the leaf; on leaf margins and leaf base; and on the petioles and stem. They are either sunken or raised. Recently, Elias (1972) has described a very large, cup-shaped petiolar nectary in Pithecellobium macradenium. Extrafloral nectaries are common in Euphor