Fungal genera: Xanthochrous [36 taxa], Xanthoparmelia [17 taxa], Xanthoria [420 taxa], Xanthoriicola [1 taxon], Xenasma [9 taxa], Xenobotrytis [4 taxa], Xenochora [1 taxon], Xenodiella [1 taxon], Xenodium [1 taxon], Xenodochus [14 taxa], Xenogliocladiopsis [4 taxa], Xenokylindria [1 taxon], Xenolophium [4 taxa], Xenomeris [5 taxa], Xenoplaca [1 taxon], Xenosporium [154 taxa], Xenostele [4 taxa], Xenostigme [1 taxon], Xenostigmella [1 taxon], Xenostomella [5 taxa], Xenotypa [1 taxon], Xerocomus [32 taxa], Xeromphalina [74 taxa], Xerotinus [3 taxa], Xerotrema [5 taxa], Xerotus [39 taxa], Xerula [23 taxa], Xerulina [1 taxon], Xiambola [1 taxon], Xiphomyces [1 taxon], Xylaria [2455 taxa], Xylobolus [68 taxa], Xylobotryum [20 taxa], Xylochora [1 taxon], Xylocladium [2 taxa], Xylocoremium [5 taxa], Xylodon [3 taxa], Xylogramma [3 taxa], Xylographa [23 taxa], Xylohypha [24 taxa], Xylomyces [3 taxa], Xylopezia [4 taxa], Xylophallus [1 taxon], Xylosorium [2 taxa], Xylosphaera [33 taxa], Xylosphaeria [1 taxon], Xylostroma [1 taxon], Xyphium [1 taxon], Xystozukalia [3 taxa]