We describe and illustrate Microsorum whiteheadii (Polypodiaceae), endemic to limestone outcrops in Sumatra. It appears related to the widespread and polymorphic M. punctatum (L.) Copeland but differs from that species by the shortercreeping rhizomes, more succulent, thicker, very dark green, oblanceolate blades, prominent hydathodes adaxially, and less visible venation. Reggie Whitehead, a fern enthusiast and grower in the Miami area, has drawn our attention to a remarkable new Microsorum from Sumatra, growing epipetrically on limestone cliffs. In the recent treatment of this genus for Flora Malesiana (Bosman et al., 1998), and also in Bosman's (1991) previous monograph of Microsorum, M. whiteheadii would appear to key to M. punctatum (L.) Copeland, but we believe M. whiteheadii is quite dramatically different in several characters, discussed below. This attractive new species is now being successfully grown and propagated (from spores) by Mr. Whitehead in the Miami area and by John Banta, in Alva, Florida (near Ft. Myers), and we honor Mr. Whitehead's efforts by naming this fern for him. Both growers were led to the same area by Tang Fook Leong, on an expedition to relocate Amorphophallus hirsutus Teijsmann & Binnendijk (Araceae). Microsorum whiteheadii A. R. Smith & Hoshizaki, sp. nov. TYPE: Sumatra. Western Sumatra, Prov. Paya Khumbu, Koto District, 30 km from Bukit Tinggi, Tanjung Gadang Rumah (near Paya Khumbu), 900 m, 2 July 1997, Reggie Whitehead s.n. (holotype, UC; isotypes, BO, L, MO, US). Figure 1. Differt a M. punctato rhizomatibus breviter repentibus internodiis 2-5(-7) mm longis, laminis succulentioribus crassioribus oblanceolatis vel spathulatis abrupte reductioribus proximaliter, prominentioribus hydathodis adaxialiter, venis lateralibus vix visibilibus in statu vivo, venis areolatis non visibilis. Rhizomes terete, in living material medium green (not glaucous) below the scales, ca. 5-10 mm thick, short-creeping, internodes 2-5(-7) mm long, roots densely set and forming a thick mat; vascular strands numerous, lacking sclerified sheaths but with numerous sclerenchyma strands (> 100) scattered uniformly throughout the cortex; rhizome scales brownish, lacking a lighter colored or hyaline margin, clathrate, pseudopeltate, appearing peltate by virtue of overlapping basal auricles, moderately dense, ovate with an attenuate tip, 3-5 X 1.5-3 mm, the bases appressed, the tips often squarrose, margins erose-denticulate to coarsely dentate or with scattered 1to 3-celled glandular hairs, otherwise glabrous, the basal cells ? isodiametric, the cells at the attentuate tip rectangular, up to 2-3 times longer than wide and often darkerand thicker-walled than walls of basal cells. Fronds monomorphic, sessile, thick-coriaceous and somewhat succulent (like India rubber plant, Ficus elastica Roxburgh). Stipes absent or less than 1 cm long, up to ca. 5 mm diam., with ca. (3-)4-6(-9) round vascular bundles arranged in a cup in cross section (two adaxial bundles much larger than the others), glabrescent or with a few linear-lanceolate clathrate scales at the very base; stipes of young fronds beset with evanescent scales. Blades simple, broadly to less often narrowly oblanceolate, mostly 20-65(-78) X 7-9(-13) cm, margins entire, base abruptly narrowed and with a narrow laminar wing nearly or quite to the rhizome, the wing ca. 1 cm or less for 10(-25) cm, blade tips rounded to subacute or acuminate; abaxial surfaces glabrous or glabrescent at maturity, when young with a scattering of minute 1to 3-celled uniseriate glandular hairs; blades of newly formed croziers covered with glandular hairs like those of stipes. Venation (of large and fully developed fertile and sterile fronds) type 4 (terminology of Nooteboom, 1997: 262-263), with the first connecting veins (between main latNOVON 10: 411-414. 2000. This content downloaded from 207.46.13.124 on Sun, 11 Sep 2016 05:09:33 UTC All use subject to http://about.jstor.org/terms