Based on palynological studies, the Irati Formation is generally correlated with the Ecca and Raniganj formations of África and índia, respectively, whereas studies on Gondwanic eusteles indicate similarities with a lower horizon corresponding to the White-Band of South África and Barakar of índia. In a previous article, the soienoid biozone that emphasizes this result was discussed. Now a new set of fóssil plants is distinguished whose biozone coincides approximately with that of the soienoid group and thus seems to present the same difficulty for correlation. This set of plants comprises eusteles showing lacunae and diaphragms in their piths which display definite developmental parameters that clearly point to their inherited, or genetic, relationship. The distribution of plants with pith diaphragms in sequences so far apart in Gondwana certainly implies the close likeness of unusual environmental condi ti ons which also must have evoked adaptive responses in the vegetative body of the plants, such as xeromorphic adaptations for aeration or water storage in the anatomical plans peculiar to each genus, associated or not with sclerenchyma. The evidence therefore points to a set of highly specialized plants growing near small basins of restricted circulation under intermittent to markedly periodic conditions of scarce aeration or brackish or saline waters
