Picobryum, a new genus of Pottiaceae (Bryophyta) from South Africa, and an erratum for Acaulonopsis Richard H Zander1, Terry A Hedderson2 1Missouri Botanical Garden, St Louis, MO, USA, 2Department of Botany, University of Cape Town, Rondebosch, South Africa A new genus, Picobryum (Pottiaceae, Bryophyta), including one new species, Picobryum atomicum,is described from the western Cape Province of South Africa. The new taxon is somewhat similar to Syntrichia gametophytically but differs in the trait combination: stem very short, central strand absent; leaves strongly reflexed to squarrose when moist, usually folded longitudinally on one side, bases sheathing, margins plane throughout, irregularly and weakly bordered in 1(–2) rows with somewhat thick-walled, less papillose cells; papillae large, simple to bifid, 1–2 per lumen; paroicous; seta essentially absent; capsule cleistocarpic, globose, and short-apiculate; calyptra mitrate. Locality data for the type of Acaulonopsis fynbosensis R.H.Zander & Hedd. are corrected in an erratum. Keywords: Allometry, Conservation, Fynbos, Picobryum atomicum, Pottiaceae, South Africa, Syntrichia The Cape Floristic Region of South Africa continues elongatas et parietibus crassis praeditas gradatim to reveal evolutionary novelties among the mosses, transientes; paroicae; seta nulla; capsula cleistocarpica particularly in the family Pottiaceae. Another taxon globosa brevi-apiculata; calyptra mitriformis. distinct at the genus level was discovered among Plants very small, gregarious, light-green and com- bryophyte collections made in the lowland Leipold- monly reddish. Stem not branching, ca 0.05–0.1 cm tville Sand Fynbos, a distinctive South African habitat long, transverse section rounded-pentagonal, central endangered by agriculture and invasive species. strand apparently absent, central cylinder of large Although South Africa has been floristically fairly cells, cortex of several layers of orange cells with well examined for bryophytes, this taxon has been weakly thickened walls, sclerodermis and hyaloder- apparently overlooked because of its small size mis absent; axillary hairs ca 3–5 cells in length, basal together with the unusual habitat. It is published here cell brownish and more thick-walled than the distal as a taxon of conservation concern. cells; rhizoids common at stem base. Leaves ap- Picobryum atomicum R.H.Zander & Hedd., gen. et pressed below and spreading when dry, often long- Published by Maney Publishing (c) British Bryological Society sp. nov. (Figure 1). itudinally broadly recurved on one side of leaf but Plantae perpusillae, gregariae, in materia naturali incurved on other side of leaf so as to form an ‘S’ in aurantiacae etiam in KOH reagentes; caulis tantum section, strongly transversely reflexed or squarrose 0.05 cm longus, filo centrali carens; folia madida valde when moist, ovate, 1.2–1.5 mm in length, upper reflexa vel squarrosa, interdum longitudinaliter in latere lamina broadly channelled to weakly keeled, leaf altero incurvata et in altero recurvata, basi vaginanti, margins plane throughout, distal laminal margins marginibus ubique planis, saepe irregulariter leniterque entire or serrulate by hollow papillae to occasionally per series 1(–2) e cellulis saepe elongatis 2 : 1 parietibus distantly dentate above, often irregularly and weakly crassiusculis minus papillosis compositas marginata; bordered in 1(–2) rows with somewhat thick-walled, costa strato stereidarum unico complanato praedita, less papillose cells, these often elongate 2 : 1; apex interne leniter distincta, interdum paene homogenea; broadly acute and mucronate, base elliptical and papillae laminae medianae atque distales magnae, sheathing stem; costa narrow but widening distally simplices vel bifidae per lumen 1–2(–3); cellulae basales and bulging slightly on both sides near apex, hyalinae, per cellulas brevi-rectangulas medialiter ad excurrent as a broad, sharp or often rather blunt mucro of several cells, these smooth or papillose, or rarely percurrent, superficial cells elongate both Correspondence to: R H Zander, Missouri Botanical Garden, PO Box 299, St Louis, MO 63166, USA. Email: [email protected] ventrally and dorsally, papillose above midleaf, 3–4 ß British Bryological Society 2011 130 DOI 10.1179/1743282011Y.0000000003 Journal of Bryology 2011 VOL.33 NO.2 Zander and Hedderson Picobryum, a new genus of Pottiaceae from South Africa Figure 1 Picobryum atomicum. 1–3. Habits. 4–7. Leaves. 8–9. Leaf apices. 10. Leaf margin near base. 11. Transverse section at mid-leaf. 12. Costal section in distal portion of leaf. 13. Calyptra. 14. Capsule, paroicous inflorescence and calyptra. Scale bars: A50.5 mm, 1–3; B50.5 mm, 4–7; C550 mm, 8–13; D50.3 mm, 14. rows of cells across costa ventrally at midleaf, quadrate, 35–40 mm in diameter, walls thin, stomata transverse section circular to elliptical, essentially apparently absent; annulus and peristome teeth homogeneous or sometimes interpretable as stereid absent. Calyptra mitrate, smooth, 350–370 mmin bands ventrally absent, dorsally present, of 3–4 length. Spores 25–32 mm in diameter, weakly papil- stereid cells in 1–2 rows, ventral epidermis not or lose (immature). Laminal KOH colour reaction Published by Maney Publishing (c) British Bryological Society weakly differentiated, of cells of slightly wider orange. lumens, guide cells 2 in 1 layer but little different Type: South Africa, Western Cape Province, Olip- from stereids, hydroid strand absent; upper laminal hants River Mountains, Porterville Area, Beaverlac, cells rounded-quadrate to irregularly rhomboid, ca road between campsites and Oliphant’s River, along 12–15(–18) mm in width, 1(–3) : 1, walls evenly Ratel’s River, 32u529270S, 19u059100E, disturbed thickened, strongly convex on both sides, papillae areas and patches of clayey mineral soil in fynbos, large but not crowded, 1–2 per lumen, simple or ca 300 m elevation, T.A.J. Hedderson 13969a,23 bifid, usually solid or sometimes hollow; basal cells June 2001 (holotype: BOL; isotype: MO); same differentiated across base, merging gradually into locality, T.A.J. Hedderson 13964,23June2001 upper cells, near insertion short-rectangular and thin- (paratypes: BOL, MO). walled, 17–25 mm wide, 2–4 : 1, grading distally into The genus name reflects the minute size of the narrowly rectangular and thicker walled cells near plants (Ital., piccolo, small; in the International leaf middle, these to 7 : 1. Paroicous. Perichaetia System 10212, pico being smaller than nano but larger terminal, inner leaves enlarged and closely sheath- than femto); the epithet reflects the difficulty of ing capsule, lower cells hyaline. Seta essentially sectioning the stem (Gk., a not, tomos cut). absent. Capsule cleistocarpic, globose and bluntly The important characters that in combination short-apiculate, to 0.4 mm (immature) in diame- distinguish this genus from similar genera (especially ter, transparent green, exothecial cells irregularly Syntrichia Brid.) in the Pottioideae are small plants Journal of Bryology 2011 VOL.33 NO.2 131 Zander and Hedderson Picobryum, a new genus of Pottiaceae from South Africa (1–3 in Figure 1), gregarious, orange; stem only thin-walled), Microbryum Schimp. (papillae several 0.05 cm long, with central strand apparently absent; per lumen, lamina with deep red reaction to KOH), leaves strongly reflexed to squarrose when moist (4–7 Phascopsis I.G.Stone (costa massive, upper lami- in Figure 1), usually curved longitudinally in different nal cells thin-walled, multipapillose), and Stonea directions on each side (11 in Figure 1), 1.2–1.5 mm R.H.Zander (strongly concave lamina, often swollen long, leaf bases very broad for the length of the leaf costa). A recently described much reduced genus, and sheathing, margins plane throughout, occasion- Neophoenix R.H.Zander & Du¨ring, also from south- ally dentate above (8 in Figure 1), often irregularly ern Africa, differs in its trichostomoid leaves with and weakly bordered in 1(–2) rows with somewhat multipapillose upper laminal cells and basal cells that thick-walled, less papillose cells, these often elongate reach up the margins, commonly merging with a 2 : 1 (8–10 in Figure 1); costa usually of nearly indistinct border of less papillose, somewhat elongate homogeneous cells with epidermal cells sometimes cells, and has much the same aspect as Aschisma with wider lumens (11 and 12 in Figure 1); upper Lindb. (Zander & During 1999) Although Neophoenix laminal cells medially rounded-quadrate to rhomboid, has transparent capsules, the opacity of the capsule wall rather small, ca 12–15 mm in width, 1 : 1, with evenly of the new genus cannot be ascertained with certainly thickened walls, papillae large, simple to bifid, 1–2 per because of the immature sporophytes. lumen; hyaline, short-rectangular basal cells grading Syntrichia may be viewed as a fairly recent taxon to elongate, thick-walled cells medially; paroicous; seta because a reduction series (assuming no reversibility) absent; capsule cleistocarpic, globose and short- is not yet evident though many species occur in arid apiculate with a mitrate calyptra (13 and 14 in lands. It might well be that Picobryum is an extremely Figure 1). There was nothing found with these trait strongly reduced taxon rapidly evolved from an combinations in the literature or in collections at BOL immediate Syntrichia ancestor in response to some or MO. extreme selective pressure in South Africa. This same Picobryum atomicum is apparently closely related pressure, unique to South