The wood and bark anatomy of all three species of Hypocalyptus fromthe monotypic South African endemic tribe
Hypocalypteae were studied. Despite large morphological differences (especially in habit) the species were
found to be similar in wood and bark structure. Discontinuities are quantitative only, relating mainly to differences
in growth form between H. oxalidifolius, a short-lived shrublet, and the two other species, H. coluteoides
and H. sophoroides, both of which are erect shrubs or small trees of up to 6 m tall. Hypocalyptus wood has a mesomorphic
structure with vessels solitary or in small groups, reflecting relatively moist habitats in fynbos
vegetation. In contrast to many genera of Leguminosae for which data are available, crystals are absent
from the wood. This is the first report of tanniniferous tubes in the wood of Leguminosae (previously reported
only in Myristicaceae and a genus from Ulmaceae). The presence of tanniniferous tubes and the
absence of crystals in all three species of Hypocalyptus underline the isolated position of the genus and
support its tribal status.