- 5 - nyi. (Kov.) Czecz., Q.pliovariabilis Kolak., Q.pseudocastanea Go- epp., Q.sosnowskyi Kolak. The roburoid oaks in Sarmatian layers were represented by single finds of the leaves of the Quercus petraea type. Already in the Pontian the ancestral form of the present-day Q.hartwissiana, described originally as Q.kodorica Kolak., was widespread. The existing roburoid oaks of the Q.ibe- rice type appeared only from the Upper Pliocene. On the way from the Datcha village to the mountains we shall draw attention to a very interesting phenomenon - a successful acclimatization of a number of adventive plants in the lowlands of Abkhazia. Around the motor-road itself, rather extensive thi- ckets of the shrub Baccharis halimifolia are seen which have de- veloped from single individuals found here in 1939.Similarly, the glass Andropogon virginicus, noticed for the first time in 1945, is now widely spread throughout Abkhazia, especially on wet pod- zol soils. Altogether about 150 species of adventive plants have been recorded in Abkhazia. Some of them arrived very long ago and became a part of the forest vegetation (Arthroxon hispidulus, Op- lismenus undulatifolius, Microstegium imberbe). Others appeared in the present century, in the period when introduction of the valuable economic plants from various countries of the world has been particularly intense. Among these are species of Paspalum for instance, which are especially widespread in Abkhazia. In re- cent years Erechtites valerianifolia, Physalis angulata, Tagetes minuta have spread rapidly. The greatest percentage of naturali- zed adventive plants originates from America, but many of them come from East Asia and the Mediterranean region. Proceeding from Sukhumi we clearly distinguish two systems of terraces in the general relief of the country, especially to the south of Gyulripsh: Tertiary terraces at 100-200 m and a lo- wer Quarternary one on which the road passes toward the Abkhazian Atara village. The Tertiary terraces, eroded by the gorges of many small rivers, are composed primarily of deposits of the Pon- tian and higher, of the Cimmerian. The last strata are usually mantled by thin proluvial - deluvial deposits, e.g. the Upper Pliocenic and younger strata on the Sukhumi mountain, where the remains of fossil plants have been found. At that time there pre-