Abstract. P. Delforge.- Contribution to the knowledge of the Orchids of the Province of Burgos (Castilla-LeŚn, Spain) [Natural. belges (Orchid. 8) 76 (1995): 232-276]. Research in the northern parts (southern piedmont of the Cordillera Cantabrica and upper Ebro basin) and eastern parts (Sierra de la Demanda and its periphery) of the Province of Burgos has revealed 55 orchid species, of which 15 new for the Province: Coeloglossum viride, Epipactis campeadorii (sp. nov.), E. parviflora, E. tremolsii, Gymnadenia odoratissima, Limodorum trabutianum, Ophrys castellana, O. dyris, O. passionis, O. sphegifera, O. vasconica, Orchis conica, O. langei, O. morio, O. tenera, and Serapias vomeracea. The presence of Cephalanthera longifolia, Epipactis atrorubens, E. microphylla, Orchis cazorlensis, O. coriophora, and Serapias cordigera is confirmed. Three interspecific hybrids have also been found. The province of Burgos is now known to harbour 60 and perhaps 61 orchid species and 5 hybrids. A special attention is granted to the systematics of genus Epipactis and the Ophrys scolopax group. An updated list of species is provided as well as the list of 262 localities prospected in June 1992, 1993, 1994, and 1995.

Key-words: Flora of Spain, Castilla-LeŚn, Province of Burgos, Sierra de la Demanda, Cordillera Cantabrica. Orchidaceae, Epipactis, Ophrys, Orchis.