Additions to the flora of the Czech Republic. XX.

This twentieth part of floristic contributions summarizes the data of taxa newly discovered in the Czech Republic – Asplenium adiantum-nigrum var. silesiacum, Calamagrostis rivalis, Callitriche ×nyrensis, Microthlaspi erraticum, seven nondescribed hawkweeds hybrids (Pilosella aurantiaca × P. bifurca, Pilosella aurantiaca × P. leptophyton, Pilosella aurantiaca × P. rothiana, Pilosella aurantiaca × P. visianii, Pilosella floribunda × P. rubra, Pilosella iserana × P. rubra, Pilosella lactucella × P. rubra), Pilosella derubella, Rubus silvae-bavaricae and Taraxacum leucopodum and data of alien species found in the Czech Republic for the first time (Acaena microphylla, Adiantum capillus-veneris, Althaea taurinensis, Aralia cordata, Cardamine occulta, Caryopteris ×clandonensis, Cerastium subtetrandrum, Cotoneaster multiflorus, C. splendens, Crepis pulchra, Eclipta prostrata, Euphorbia nutans, Kitaibelia vitifolia, Muhlenbergia mexicana, Panicum schinzii and Selaginella kraussiana). Furthermore, critically endangered species (according to the Red List of Vascular Plants of the Czech Republic) are reported from new localities (e. g. Ajuga chamaepitys, Artemisia scoparia, Botrychium matricariifolium, Campanula cervicaria, Chenopodium murale, Conringia orientalis, Cuscuta approximata, Epipactis leptochila, Geranium divaricatum, Lactuca saligna, Nasturtium microphyllum, Nuphar pumila, Papaver lecoqii, Pyrola chlorantha, Rubus lividus and Valerianella rimosa). Finally, less rare and threatened species are reported from phytogeographical districts where they had not been recorded yet (Alchemilla cymatophylla, Androsace elongata, Hieracium glaucinum, Thesium alpinum and Veronica anagalloides).