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The flora and vegetation of the Tremiti Islands have been the subject of several important studies. The work of GASPARRINI (1837) represents a milestone containing, as it does, the first list of 171 species present on the islands and identifies the presence of Centaurea diomedea. TERRACCIANO (1890) further contributed to the knowledge on the flora of the islands, describing 221 species in total, publishing the results of surveys carried out by TELLINI (1890), also responsible for geological research on the islands. Another boost to floral research on the islands was provided by CORTESI (1909), but the most important contribution to the knowledge of the flora of the islands is that of BEGUINOT (1909-1910), with the publication of two important studies that were the fruit of seven years of research. The first phytosociological study of the vegetation of the Tremiti Islands concerned Pianosa (CRISTOFOLINI, LAUSI, TARABOCCHIA and PIGNATTI, 1967) and mainly dealt with the halo-nitrophylic aspects of the vegetation, also completed by an accurate study of the flora, showing it to the rather poor in species. The most complete study of the vegetation on the Tremiti Islands is that carried out by DE MARCO, VERI and CANEVA (1984), which remains a point of reference to this day. This study of the islands also analyzes the environmental transformations that occurred in the period 1955-1981. The key point of this work is that they analyzed and arranged all the principal aspects of the vegetation, some of which then became the subject of further investigation by other authors. WIELBACH (1985) published a brief list of the spontaneous orchids of the Tremiti Islands observed in April 1983, reporting: Ophrys sphecodes Mill. subsp. incubacea white, Ophrys sphecodes Miller subsp. garganica Nelson, Ophrys tenthredinifera Willd., Ophrys lutea Cav., Ophrys bombyliflora Link, Orchis morio L., Orchis papilionacea L., Orchis purpurea L., Barlia robertiana Loisel, Serapias vomeracea Briq. As for the halo-nitrophylic vegetation of the Tremiti Islands, a fundamental contribution was made by BIONDI (1988) who highlighted the presence of several new associations. One type of halo-nitrophylic vegetation characterized by the presence of fruticose plants such as Artemisia arborescens, Atriplex halimus and the suffrutex Suaeda vera come together in the Atriplici halimi-Artemisietum arborescentis association, which can be found both on S. Nicola, near the ancient convent, and on Caprara. Another halo-nitrophylic association has grown up near the sea in the zone reached by saltwater spray and defined as Suaedo verae-Atriplicetum halimi. Both these associations come into the Pegano-Salsoletea class Br.-Bl. et Bolos 1957. A third type of halo-nitrophylic vegetation is found on the island of S. Nicola, in the area exposed to the South and in contact with the Mediterranean maquis formation, it is thermophytic and defined as Oleo-Euphorbietum dendroidis Trinajstic subassociation Atriplicetosum halimi. This new subassociation belongs to the Oleo-Ceratonion alliance. The finding of Limonium diomedeum is due to the specialized study of BRULLO (1988), that collected the first samples used for its diagnosis at Punta Diamante, on S. Domino, distinguishing it from Limonium cancellatum (Bertol.) O. Kuntze with which it had previously been confused. On the basis of the identification of this new species, BARTOLO, BRULLO e SIGNORELLO (1989) successively identified a new halophytic plant association for rocky environments, the Crithmo-Limonietum diomedei, belonging to the Crithmo-Limonietea class Br.-Bl. 1947. This association, found along the bays of the cliffs on the Tremiti Islands and on the rocky shore of the Gargano, is characterized by the dominance of Limonium diomedeum, Crithmum maritimum, Lotus cytisoides, Silene sedoides L., Allium commutatum Guss., Limonium virgatum (Willd.) Fourr. etc. At the base of the high rocky cliffs, the latter is substituted by a subassociation known as plantaginetosum, for the presence of Plantago holosteum Scop. sp. scopulorum (Degen) Horvatic. The study of the halophytic rock vegetation, an environment characterized by a fairly specialized flora, was furthered in the same year (DE MARCO and BRULLO, 1989). The Anthyllido-Centauretum diomedeae association has been found on the high cliffs of S. Domino and S. Nicola. Apart from Anthyllis barba-jovis, a pioneer species typical of halophytic coastal environments, this association also consists of endemic species such as Centaurea diomedea Gasparrini, Aurinia leucadea (Guss.) Koch and Asperula staliana Vis. subsp. Diomedea. This latter subspecies has become established recently (KORICA, LAUSI & EHRENDORFER, 1992) from samples collected on S. Domino and successively also found on S. Nicola. It is a trans-Adriatic species that has become differentiated into several subspecies after long periods of isolation. BIBLIOGRAPHY CONCERNING VEGETATION BARTOLO G., BRULLO S., SIGNORELLO P. (1989) - La classe Crithmo-Limonietea nella penisola italiana. Colloques phytosociologiques 19:55-81 BEGUINOT A. (1909) - Materiali per una flora delle isole Tremiti. Bollettino Società Botanica Italiana anno 1909: 200-212 BEGUINOT A. (1910) - La vegetazione delle isole Tremiti e dell'isola di Pelagosa. Studio fitogeografico. Memorie della Società Italiana delle Scienze (detta dei XL), serie 3, tomo 16:1-69 BIONDI E. (1988) - Aspetti di vegetazione alo-nitrofila sulle coste del Gargano e delle isole Tremiti. Archivio Botanico e Biogeografico Italiano 64:19-33 BRULLO S. (1988) - Miscellaneous notes on the genus Limonium (Plumbaginaceae). Willdenowia 17:11-18 CORTESI F. (1909) - Contribuzione alla flora delle Isole Tremiti. Annali di Botanica, Vol. VII, fasc. 3, pp. 489-502. CORTESI F. (1910) - Nuova contribuzione alla flora delle Isole Tremiti. Annali di Botanica VIII. CRISTOFOLINI G., LAUSI D., TARABOCCHIA M., PIGNATTI S. (1967) - Flora e vegetazione dell'isola di Pianosa (isole Tremiti). Giorn.Bot.Ital.101:189-198 DE MARCO G., CANEVA G., VERI L. (1984) - Analisi fitosociologica, cartografia della vegetazione e trasformazioni ambientali nel periodo 1955-1981 delle isole Tremiti (Adriatico centro-meridionale). Annali di Botanica. Studi sul territorio, suppl.2:17-47 GASPARRINI G. (1837) - Descrizione delle isole Tremiti e del modo come renderle coltive. Annali Civili del Regno delle due Sicilie 15:79-105 KORIKA B., LAUSI D., EHRENDORFER F. (1992) - A new subspecies of the trans-Adriatic Asperula staliana from the Isole Tremiti: subsp. diomedea, and its ecology. Flora Mediterranea 2:65-76 LAUSI D. (1971) - La vegetazione delle isole Tremiti. Relazione preliminare delle ricerche sulle popolazioni insulari compiute nel triennio 1965-1968. C.N.R. Quaderni de La Ricerca Scientifica 73:59-60 PAMPANINI R. (1916) - Una collezione botanica delle Isole Tremiti. Boll. Soc. Bot. Ital. 2. PIGNATTI S. (1971) - Problemi fitogeografici collegati al popolamento vegetale delle Isole Tremiti. Quad. Ric. Sc. C.N.R. Roma 73, pp. 61-62. TERRACCIANO A. (1890) - La flora delle isole Tremiti. Nota preliminare. Giornale Botanico Italiano 22:383-390 WIEBALCK S. (1985) - Orchideenausflug zu den Inseln Tremiti nordlich vom Gargano. Berichte aus den Arbeitskreisen Heimische Orchideen 2:140-141.