Pteridofitas extintas o raras del Valle de México

the valle de méxico have 113 species of pteridophytes, 18 species are extinct in the zone and 19 species are rare or few frequent, belong 23 genera and 37 species according iucn (1994). we revised 1400 specimens of pteridophytes collected in fiels and exemplaries of national and international herbarium as encb, mexu, chapa, p, k, lp, si, mo. we found some species which were living in the zone in the century xix and first middle century xx and now these species there are not in the area as adiantum capillus-veneris l., asplenium exiguum beddome, asplenium palmeri maxon, blechnum glandulosum kaulf. & link, cheilanthes mexicana davenp., cheilanthes microphylla (sw.) sw., cheilanthes notholaenoides (desv.) maxon & weath., pityrogramma ebenea (l.) proctor, polypodium polypodioides (l.) watt var. aciculare weath., polypodium rosei maxon, psilotum nudum (l.) beauvais, selaginella peruviana (milde) hieron., selaginella wrightii hieron., selaginella arsenei weath., terpsichore delicatula (m. martens & galeotii) a.r. sm. and woodsia mexicana fée, the vouchers of these specimens were realized in place now occupied by colonies and commercial centers. the aquatic habitats and the aquatic pteridophytes were disappearing as azolla mexicana c. presl, marsilea mollis b.l. robinson et fernald. some species as anogramma leptophylla (l.) link, asplenium fibrillosum pringle &davenp. & davenp., athyrium bourgeaui e. fourn., blechnum stoloniferum (mett. & e. fourn.) c. chr., bommeria subpalacea maxon, botrychium schaffneri underw. var. schaffneri, campyloneurum amphostenon (kunze & klotzsch) fée, elaphoglossum engelii (h. karst.) h. christ., elaphoglossum erinaceum (fée) t. moore var. occidentale mickel, elaphoglossum glaucum t. moore, elaphoglossum minutum (pohl & fée) t. moore, iso？tes mexicana underw., pecluma alfredii (rosenst.) m.g. price var. cupreolepis (a.m. evans) a.r. sm., plagiogyra pectinata (liebm.) lellinger, polypodium californicum kaulf., polystichum fournieri a.r. sm., po