Abstract

The Permian and Triassic floras of southern areas show striking differences. Glossopteris is a dominating element in the Permian, and Dicroidium commonly is dominant in the Triassic. The southern plants also contrast with contemporary floras of the north. Coniferophytes shared the ancient division into northern and southern groups, a division which still persists. Fossil southern plants probably were derived from older groups of plants of northern regions. Two periods of land-plant intercommunication between northern and southern areas seem indicated. Isolation could most readily be explained if only brief connections formed across the epicontinental Tethys. Intercommunication may have occurred in the Carboniferous and very late in the Permian. Dating periods of floral transfer would help in correlation. Floral differences near the Permian-Triassic boundary do not indicate points of origin or extinction for groups of plants. Abrupt displacement of the Glossopteris flora by a Dicroidium flora very early in the Triassic is not fully explained but may be clarified with the aid of palynology. For stratigraphic purposes, records of southern plants must continue to be interpreted in relation to a zonation based on marine fossils.