RESUMENCon base en la recolección de ejemplares botánicos en diferentes regiones del estado de Hidalgo y en el estudio de material herborizado depositado en diversas colecciones institucionales, complementado con una revisión bibliográfica, obtuvimos el inventario de la flora epifítica vascular de la entidad. Como resultado de lo anterior se registran para el área de estudio 17 familias (nueve de ellas pertenecientes a las Pteridofitas y el resto a las Magnoliofitas), 64 géneros y 163 especies. Asimismo, se aportan datos sobre la distribución municipal de los taxa y un análisis sobre su representación por tipo de vegetación y por intervalo altitudinal. Se registran por primera vez para el estado los siguientes taxa: Tillandsia filifolia Schltdl. & Cham., T. heterophylla E. Morren, Pleurothallis sp. 1 y Pleurothallis sp. 2. Sólo Laelia gouldiana Rchb. f., Dignathe pygmaeum Lindl. y una especie no descrita del género Goodyera son endémicos del estado.Palabras clave: distribución, diversidad de especies, epífitas vasculares, Hidalgo, México. ABSTRACTBased on the recollection of botanical specimens in different regions of the state of Hidalgo and the study of herbarium material deposited in several institutional collections, supplemented by a literature review, we obtained records of 17 families (nine of them belonging to Pteridophytes and the rest to Angiosperms), 64 genera and 163 species. We also provide data about the municipal distribution of taxa and an analysis of their representation by

The vertical structure of fern spore banks was studied in a xerophilous shrubland, montane rain forest, and pine-oak forest in Hidalgo, Mexico, using the emergence method. Soil samples were collected in April 1999 at depths of 0-10, 10-20, and 20-30 cm. Viable spores decreased significantly with depth in all vegetation types, and the highest number of prothallia and sporophytes was found in the uppermost layer. The montane rain forest and the xerophilous shrubland had the largest and the richest banks, respectively. Twenty-three fern taxa were registered in the aboveground vegetation, 12 in the soil banks, and 43.5% were in both. Aboveground and in the soil bank, the xerophilous shrubland, the montane rain forest, and the pine-oak forest had, 17 and 7, 1 and 6, and 7 and 3 taxa, respectively. These were distributed differentially in relation to depth. The Sørensen index indicated a similarity of 61.5% between the xerophilous shrubland and the montane rain forest, and the Czeckanovsky index indicated 19.75%. The presence of viable spores in the soil of all vegetation types confirmed the existence of natural spore banks. Long-distance dispersal was an important factor determining the specific composition of the xerophilous shrubland and the pine-oak forest.

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A comparative study of the gametophytes of eight Mexican species of the genus Blechnum (Blechnaceae) is described. Fertile plants for spore collection were obtained at different Mexican localities. The spores were sown in agar enriched with Thompson media and cultured at 22-25 °C, with a light regime of 12 hours. Spores of all species are monolete, ellipsoidal to spheroidal, and non-chlorophyllous. Vittaria-type germination occurred after 6-14 days followed by a 2-6-cell-long filament and Aspidium-type prothallial development. Adult gametophytes are cordiform-spatulate to cordiform-reniform and have wide wings with numerous unicellular marginal and superficial hairs. Sporophytes developed only in B. occidentale and B. polypodioides.

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