P o l y s t i c h u m m i n u t i s s i m u m s p . n o v. ( s e c t . Haplopolystichum, Dryopteridaceae): The smallest Polystichum found in a karst cave in China

(ReceivedJune�9,�2008;�AcceptedFebruary�12,�2009) ABSTRACT. � Polystichum minutissimum (sect.� Haplopolystichum,� Dryopteridaceae)� fromakarstcavein� southernGuizhou,�China,�isdescribedasnew.�Polystichum minutissimum isthesmallestspeciesinthegenus.� ItismorphologicallymostsimilartoP. liboense,� aspeciesalsodescribedfromalimestoneareainsouthern� Guizhou,� butdiffersfromP. liboenseinlackinghydathodesnearthemarginofthepinnae.�Additionally,� P. minutissimum hasmuchsmallerlamina�(1.3-3.8��0.7-1.1�cm)�andpinnae�(middleones�2.9-5.8��2.8-4.5�mm).� Infact,� ithasthesmallestlaminaandpinnaeinthegenus.� Polystichum minutissimum growsincool,� moist,� andtwilightconditionsinacave,� whereitcanbeextremelysensitivetoenvironmentalchanges,� thereby� raisingconcernforitsconservation.