Abstract. Delforge, P. - Contribution to the knowledge of the Orchids of the island of Samos (Eastern Aegean, Greece) [Natural. belges 89 (Orchid. 21) (2008): 71-251]. After a presentation of the geology, the geomorphology, the human impact over the landscape, and the vegetation of the island of Samos, a review of the past and present studies about Samian orchids is made. It appears that 54 orchids species were known for Samos around the year 1992 (Table 1). The negative repercussions of the recent climatic changes on the eastern Aegean orchid flora and of the big forest fires of 2000 on Samos are evoked. Research in Samos in March, April, and May 2008 has revealed 59 orchid species for the island, bringing their number up to 61 (Table 2). Among the 61 species certainly known for the island of Samos, one is very likely extinct (Cephalanthera epipactoides), one, not seen in 2008, is represented by only one or few individuals very sporadic (Ophrys lesbis), and one, probably endemic, is nearly extinct (Dactylorhiza pythagorae). Two species, Ophrys basilissa and O. omegaifera are represented by few individuals in flowers in 2008, growing each on one single site, and 9 others are present in only 1-2/406 squares of 1 km × 1 km: Epipactis condensata, E. microphylla, Ophrys cerastes var. minuscula, O. ceto, O. homeri, O. phryganae, O. polycratis, O. villosa (s. str.), and Neottia ovata. Discussions are made for each species observed or listed in the island of Samos, following the order used in Delforge (2006a).

The genus Cephalanthera is represented by C. longifolia (very local), C. rubra (extremely local and rare), and C. epipactoides (extremely local and rare, known from only one site, probably extinct after the big fires of 2000, which have destroyed numerous pinewoods of the island). The genus Epipactis is represented by E. microphylla (extremely local and rare, suffering from the climatic changes), E. condensata (extremely local and rare, first mention for Samos), and E. densifolia (very local, usually identified to E. helleborine or E. atrorubensbefore 2003). Limodorum abortivum is local, Neottia ovata extremely local and rare, but abundant in its 2 stations, Spiranthes spiralis, which flowers only in Octobre, known from few places, and Platanthera chlorantha extremely local.

 The genus Dactylorhiza is represented by D. romana (rather widespread only in the Ambelos, the central massif of the island), and D. pythagorae (endemic, nearly extinct, but which could represents a local settlement of D. nieschalkiorum in Samos). The genus Serapias in the island comprises S. parviflora (very local), S. bergonii (rather widespread), S. vomeracea (very local), S. orientalis var. orientalis (very local), S. orientalis var. carica (local). All the Anacamptis pyramidalis seen in 2008 belong to A. pyramidalis var. brachystachys, widespread. The genus Orchis is represented by 14 species belonging to 7 species group, (1) the O. palustris species group, with O. laxiflora and O. palustris var. elegans, both extremely local and endangered by the destruction of the rare wet biotopes, (2) the O. morio species group with O. picta var. caucasica (local); (3) the O. papilionacea species group with O. papilionacea var. heroica (very local), (4) the O. coriophora species group with O. fragrans (rather widespread), and O. sancta (very widespread, by far the most widespread orchid of the island), (5) the O. mascula species group with O. anatolica (rather widespread), O. pinetorum (rather widespread but only in the mountains), and O. provincialis (very local, only in the mountains); (6) the O. militaris species group with O. anthropophora (very local), Orchis simia (extremely local), and O. italica (rather widespread), (7) the O. tridentata species group with O. tridentata (very local, only in the mountains), and O. intacta (local).

Himatoglossum robertianum is the sole Himantoglossum species on Samos, where it is rather widespread, better represented that it is usually said.

The genus Ophrys is represented by 29 species sometimes considered, as usual, as difficult to identify. The sectio Pseudophrys on Samos comprises 11 species which belong to 6 species groups: (1) the Ophrys iricolor group with the sole O. iricolor (rather widespread), (2) the O. attaviria group with O. parosica (var. parosica, local, and var. phaseliana, much more rarer), and O. pelinaea (very local, first mention for Samos), (3) the O. blitopertha group with O. blitopertha (very local), (4) the O. subfusca group with O. cinereophila (very local, first mention for Samos), (5) the O. lutea group by O. sicula (rather widespread), and O. phryganae (extremely local), and (6) the O. omegaifera group with O. omegaifera (extremely local and very rare), O. basilissa (extremely local and very rare), O. sitiaca (very local), and the late‑flowering O. polycratis extremely local, here described.

The section Ophrys (= Euophrys Godfery nom. nudum) on Samos comprises 18 species which belong to 9 species groups: (1) the Ophrys speculum group with O. speculum (local), and O. regis-ferdinandii (very local), (2) the O. tenthredinifera group with O. bombyliflora (very local), the large flowered O. leochroma (extremely local), and O. villosa (extremely local), (3) O. apifera, very local, (4) the O. bornmuelleri group with O. heterochila (local), frequently misunderstood due to its floral variability, and the very large- and late-flowering O. episcalis var. samia (very local, scattered in the island, var. nov. here described), (5) the O. oestrifera group with O. cerastes (var. cerastes, very local, and var. minuscula, much more rarer), O. ceto (extremely local), and O. dodekanensis (very local), (6) the O. heldreichii group with O. homeri (extremely local), (7) the O. umbilicata group with O. umbilicata (local), (8) the Ophrys reinholdii group with O. reinholdii (very local), (8) the O. argolica group, represented by one or few individuals of O. lesbis, not seen in 2008, perhaps extinct, and (9) the O. mammosa group with O. ferrum-equinum (local, with very varied flowers: f. ferrum-equinum, f. labiosa, f. subtriloba, and f. minor), O. mammosa (local), and the early-flowering O. herae (very local, described from Samos in 1992).

After carefull examination of “critical” plants precisely located in the field as well as numerous photographs, published or not, it appears that numerous old or recent mentions of orchids, made for Samos, are questionable or erroneous. As a result, the following species must be deleted from the list of the orchids of the island of Samos: Cephalanthera cucullata, Epipactis atrorubens, E. helleborine, Ophrys attica, O. bremifera, O. candica, O. cerastes, O. cornuta, O. cornutula, O. cretica, O. doerfleri, O. ‘fuciflora-holoserica’, O. fusca (s. str.), O. heldreichii, O. leucadica, O. (holoserica subsp. vel var.) maxima, O. minutula, O. oestrifera, O. scolopax, O. tenthredinifera (s. str.), Orchis morio (s. str.), O. papilionacea var. grandiflora, Serapias politisii.

A list of species and 65 distribution maps, based on the presence in 406 utmwgs84 squares of 1 km × 1 km, are provided as well as a list of 586 sites prospected during the spring 2008, from March 1 to March 14, and from March 29 to May 26.

Key-Words: Flora of Greece, flora of Aegean, flora of Samos; Orchidaceae, Ophrys episcopalis var. samia P. Delforge var. nova, Ophrys polycratis P. Delforge spec. nova.