Additamenta ad floram Reipublicae Bohemicae. XVIII.

The eighteenth part of floristic contributions includes records on taxa newly discovered in the Czech Republic (Asplenium fontanum, Picris hieracioides subsp. umbellata, Rubus placidus and Spergularia echinosperma subsp. albensis), including alien species (Heracleum sosnowskyi and Proboscidea fragrans), taxa newly escaped from cultivation (Chenopodium giganteum, Delphinium grandiflorum, Erodium manescavi, Fibigia clypeata, Galanthus elwesii, G. woronowii, Juncus ensifolius, Liatris spicata, Pteris cretica and Thermopiss villosa). Finds of Rubus jarae-cimrmanii, R. perpungens, R. vatavensis, Taraxacum aspectabile, T. clandestinum and T. sparsum described from the Czech Republic as new to science, are also listed below. Furthermore, critically endangered species (according to the Red List of Vascular Plants of the Czech Republic) are reported from new localities (e. g. Anacamptis morio, Bifora radians, Centunculus minimus, Epipogium aphyllum, Erysimum repandum, Hibiscus trionum, Himantoglossum adriaticum, Juncus tenageia, Koeleria glauca, Malaxis monophyllos, Nigella arvensis, Papaver lecoqii, Pulicaria vulgaris, Samolus valerandi, Veronica opaca and V. scardica). Finally, less rare and threatened species are reported from phytogeographical districts where they had not been recorded yet (e. g. Arum maculatum, Kickxia elatine, Najas marina, Vallisneria spiralis and Xanthium albinum).