Pseudocrossidium steerei is described as a new from interandean region from province of Pichincha, Ecuador. In 1985 field work was conducted in various vegetation zones in Ecuador by I. Sastre-De Jesiws and author to gain an overview of bryophytes of that country. In part as a result of that work, a new of Pseudocrossidium was discovered from arid interandean region northeast of Quito. PSEUDOCROSSIDIUM STEEREI Churchill, sp. nov. (FIG. 1-11) Caulis filum centrale bene evolutum; folla spiraliter disposita ovato-linguata cucullata unistratosa; costa percurrens in sectione transversali e cellularum magnarum strato medio et stereidarum ventralium et dorsalium stratis composita; lamina ultra mediam adaxialiter filamentis provisa et harum cellula terminalis apice irregularis prominula; propagula sphaerica axillaria pedicello insidentia. TYPE: ECUADOR. PICHINCHA PROVINCE. Just south of Tabacundo, on road to Guayllabamba, ca. 00*00', 78*15'W, in estepa espinosa montano bajo, on xeric shrubby steppe slopes, in partly sandy soil beneath shrub, associated with Pseudocrossidium replicatum (Tayl.) Zander, ca. 2,0002,500 m, 20 vii 1985, Churchill & Sastre-De Jesfis 13494-a (holotype, NY; isotypes, AAU, B, BM, BUF, COL, DUKE, H, MEXU, MO, QCA, U). Plants terricolous, medium size, loosely caespitose, darkto brownish-green, youngest adult leaves dull green; stems erect, to 1.5 cm tall, branches absent to few, in cross section epidermal cells indistinct, small and thick-walled, rusty-red, outer cortical cells in a single distinct layer, inner cortex of large hyaline cells in 4-5 rows, central strand distinct, of many small cells; axillary hairs 4-celled, stalk cell short and brown, 3 distal cells longer and hyaline; leaves crowded, when dry appressed and helically wound about stem, often twisted to right, occasionally to left, spreading when wet, ovate-lingulate, 1.2-1.5 mm long, 0.5-0.7 mm wide, acute to obtuse, cucullate, base ovate, cuneate, margins entire, recurved in upper 1/4-1/3, plane at base, lamina unistratose; costa subpercurrent, ending 2-3 cells below apex, at leaf base 140 Em wide, in cross section at midleaf with adaxial epidermal cells forming single-celled filaments with terminal ends irregular and projecting, abaxial epidermal cells somewhat enlarged, thick-walled and rounded on surface, stereid bands distinct adaxially (1-2 layers) and abaxially (2-3 layers), guide cells large, distal costa cross section lacking adaxial stereid band; filaments at midleaf 1 cell tall, 2-3(-4) cells tall in upper 1/3 of leaf, terminal filament cell larger, irregular and variously projecting but not forming distinct papillae; median cells quadrate or subquadrate (occasionally short rectangular), thick-walled, smooth, or with slightly bulging low papillae, 4-8 um in diameter; basal cells rectangular, juxtacostal cells 30-40(-50) um long, those toward basal margin small, 15-20 um long; propagula produced on branched stalks in leaf axils, spherical, multicellular, 36-40 um diameter, golden-brown. Sexual condition and sporophyte unknown. Etymology. -This is named in honor of Dr. William Campbell Steere. The numerous accomplishments of Dr. Steere have been recounted by Buck (1986, 1989) and Crum (1977). One aspect of his career that has not been documented was Dr. Steere's willingness to determine bryophytes from Latin America. It is apparent to anyone working with collections at New York Botanical Garden that an enormous number of bryophytes, probably in thousands, from all parts of Latin America were dentified by Steere over several decades for institutions and individuals. The names of Richard Spruce and William Campbell Steere will always be associated with establishing foundation of our understanding of diversity of Ecuadorean bryophytes. Distribution and ecology.Presently known only from type locality, this is found in interandean plateau region characterized by xerophytic vegetation of grasses and shrubs, particularly on escarpments. The generic limitations of Pseudocrossidium, as modified by Zander (1979), emphasize the trend to elaboration of parts of leaf as photosynthetic organs, either in differentiation of a pad of adaxial costal filaments, as is found in Crossidium ..., or of thin-walled, hollow-papillose cells of interior of often spiral-revolute upper leaf margins ... or both elaborations may occur in same species (Zander 1979: 203). This new is closely allied to Williams' original concept of Pseudocrossidium (1915). Superficially these plants resemble 0007-2745/90/353-356$0.55/0 This content downloaded from 157.55.39.186 on Sun, 09 Oct 2016 04:14:26 UTC All use subject to http://about.jstor.org/terms 354 THE BRYOLOGIST [VOL. 93