The grikes (crevices in the limestone) provide moist shelter, supporting a wide range of plants including dwarf shrubs. Where the surface of the limestone pavement is shattered into gravel many of the hardier Arctic or alpine plants can be found, while when the limestone pavement is covered by a thin layer of soil patches of grass are seen, interspersed with herbaceous plants. Among the flowers recorded from the Burren is the spring gentian, an alpine plant with bright blue flowers that are used as a symbol for the area by the national tourist board, Failte Ireland. The Irish orchid ("Neotinea maculata" and 21 other species of orchids ) and bloody cranesbill ("Geranium sanguineum") also occur. Other notable flowers are "Anacamptis pyramidalis", "Platanthera chlorantha", "Ophrys insectifera" "Euphrasia salisburgensis", "Lathyrus linifolius", "Carlina vulgaris", "Centaurium erythraea", "Succisa pratensis", "Primula veris", "Filipendula vulgaris", "Parnassia palustris", "Campanula rotundifolia", "Helianthemum oelandicum", "Polygala vulgaris", "Saxifraga hypnoides", "Potentilla fruticosa", "Antennaria dioeca", "Primula vulgaris", "Hypericum androsaemum", "Asperula cynanchica", "Rhinanthus minor", "Blackstonia perfoliata" and "Dryas octopetala". Another prominent presence in limestone grikes are around 24 species of fern, such as the Mediterranean "Adiantum capillus-veneris".