DEVELOPMENT OF DORSIVENTRALITY IN SEEDLINGS OF AZARA-SERRATA R-AND-P (FLACOURTIACEAE)

Azara spp. generally have dorsiventral shoots with the appearance of a large and a small 'leaf' at each node. On morphological grounds the s mall 'leaf' is usually considered to be derived from an upper stipule, while the lower stipule is reduced. This interpretation is reinforced by the changes during seedling development. Seedlings usually pass th rough a phase where the shoot is radially symmetrical and trilacunar n odes with small, glandular, non-vascular stipular structures are forme d. Then nodes become more asymmetrical with the diminution of stipular development and lateral leaf trace development on one side, and accen tuation on the other, and this process proceeds until the adult state is reached. Dorsiventrality depends on alternation of asymmetry at suc cessive nodes and alternation may appear later than asymmetry. The cha nges in the seedling indicate that a recent interpretation of the adul t structure of Azara based on homoeosis is not useful. The seedlings p rovide an interesting case in continuum morphology since they show a c ontinuum of stipular structures from 'gland' through to 'leaf' but the continuum does not quite extend to the original leaf blade, which rem ains distinctive.