Primary structures in Permian wood sample from Gondwanaland frequently offer difficulties in classifyng them according to the classical view points of a formal anatomy. Many of these woods have been seen as "anomalous" because in a single thin section they may exibit both endarch and mesarch configurations. As a result, palaeobotanists have made many observations on these peculiarities but the descriptions have not resolved the problem as to how these "primary elements" could appear in the mature wood, since in modern plants they only appear in seedlings. In this work the results of ontogenetic studies by Chauveau (1911) and more recently by Boureau (1938, 1951, 1953) are utilized to explain the frequency of many of the peculiar configurations in gondwanic wood genera. The ontogenetic laws of Chaveau provide the best key to understanding these structures that has been presented to date.
