Micropolypodium differs from other genera of Grammitidaceae in having segments or pinnae each with a single unbranched or 1-forked vein, erect rhizomes, linear fronds generally less than 1 cm wide, unisoriate segments, and prominent hydathodes. About 30 species are known, most in tropical America and a few in eastern Asia. New combinations are made for the known species. A list of excluded names in Xiphopteris, in which most of the species have previously been placed, is provided. Recent studies of grammitid ferns (Bishop, 1988, 1989; Smith et al., 1991; Smith & Moran, 1992; Parris, 1984, 1990) allude to the patent unnaturalness of traditional classifications of the Grammitidaceae, which have been based in large part on blade dissection. In an effort to arrive at a more natural classification of the family, studies initiated by Bishop and continued by Smith reveal that the genus Micropolypodium, established for a few Asian species, should be expanded to include many tropical American species heretofore placed variously in Grammitis (Morton, 1967), Xiphopteris (Copeland, 1952), and formerly Polypodium (Maxon, 1916). In lieu of a monographic treatment, which is needed especially for the South American species, and so that combinations are available for the forthcoming Flora Mesoamericana, I here provide a conspectus of Micropolypodium and make transfers of those species generally accepted in modern floristic accounts for Latin America (Proctor, 1977, 1985, 1989; Mickel & Beitel, 1988; Lellinger, 1989; Smith, 1981; Stolze, 1981). Following the transfers to Micropolypodium, I list all species that have been included within Xiphopteris and give their current taxonomic disposition, if known. Micropolypodium Hayata, Bot. Mag. Tokyo 42: 341. 1928. TYPE: Micropolypodium pseudotrichomanoides (Hayata) Hayata, based on Polypodium pseudotrichomanoides Hayata [ M. okuboi (Yatabe) Hayata]. Figure 1A. Plants usually epiphytic, rarely on rocks; rhizome radially symmetrical, suberect or erect, bearing golden, orangish, or yellowto orange-brown, often lustrous, nonclathrate or weakly clathrate scales that are entire, irregularly toothed, sparsely glandular, or setulose on the margin, setulae concolorous or often darker than scale body, cells of body often tumid; fronds monomorphic or nearly so, short-stipitate, with petioles 0.2-0.5 mm diam., not articulate to the rhizome; lamina linear, commonly 3-15(-25) cm long, usually less than 1(-1.2) cm wide, shallowly to usually deeply pinnatifid, pinnatisect, or barely pinnate, with usually numerous oblong to deltate, decurrent segments (pinnae), these sometimes with an acroscopic hump (segments gibbous); segments planar, basiscopic side not folded over sorus; laminar tissue chartaceous to subcoriaceous; veins simple or with only an acroscopic fertile vein branch, lacking a dark sclerenchymatous sheath except at the very base of the segment (not extending more than /o the segment length); hydathodes present, round to clavate, usually conspicuous adaxially; setae often present on axes and lamina, these maroon to redbrown; hairs simple or often branched, mostly 0.10.5 mm long, multicellular with many short cells, at times glandular, hyaline with darkened crosswalls; sori round, superficial, one per pinna, usually adjacent to midrib at base of costa or on the acroscopic veinlet, borne along most of the blade length; paraphyses absent; sporangia glabrous. The genus comprises about 30 species from southern Mexico to Bolivia and southern Brazil, and the Antilles; a few species occur in eastern Asia and Malesia (Japan, China, Sikkim, Philippines, New Guinea). Micropolypodium differs from all other neotropical genera of Grammitidaceae by having segments (pinnae) with a single unbranched vein or with only an acroscopic branch (Figs. 1, 2A) and the segments often gibbous. Additional important (but not unique) characteristics are the radially symmetric erect rhizomes (Hayata 1928a, b, 1929), the often golden brown nonclathrate rhizome scales, linear fronds usually less than 10 mm wide and often less than 6 mm wide, unisoriate segments (pinnae), prominent adaxial hydathodes (Figs. 1D, G, H, 2A), and the long, dark red-brown unbranched setae. The type is from eastern Asia, but by far the greatest diversity in the genus is in the Neotropics, with species most numerous and diverse in the West Indies and Central