BFNA Title: Pilotrichaceae
Author: P. M. Eckel
Date: May 29, 2011
Edit Level: R
Version: 2

Bryophyte Flora of North America, Provisional Publication
Missouri Botanical Garden

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Patricia M. Eckel


Plants pleurocarpous, small or slender to robust, rather soft or delicate, shriveled when dry, in loose or moderately dense, mostly flat dark green to yellow-green, dull or glossy mats. Primary stems creeping and spreading, leaves reduced, regularly or irregularly pinnately branched, moderately radiculose, sometimes in tufts; secondary stems spreading, suberect and frondose, not or sparingly branched. Stems mostly freely branched, green, more or less prostrate, not ascending, more or less radiculose, irregularly to pinnately branched; paraphyllia lacking; pseudoparaphyllia absent [filamentous]; hyalodermis present or absent, central strand absent; axillary hairs of two to several cells, commonly with an elongate hyaline distal cell, basal cell small, brown. Leaves  mostly  more or less complanate, often asymmetric and dorsiventrally oriented, somewhat dimorphic, vertical (dorsal and ventral) leaves erect, broadly oblong, oblong-ovate, to ovate-lanceolate, usually abruptly or gradually acuminate, symmetrical, lateral leaves tending narrower, erect-spreading to spreading, less symmetric; frequently bordered with elongate cells; margins often dentate; laminal cells smooth to 1-papillose, often lax to firm-walled, isodiametric or linear-rhomboidal, essentially undifferentiated in alar regions; costa double and well-developed.  Specialized asexual reproduction infrequent, by cylindric gemmae, variously in leaf axils, specialized branches, and ventrally on stems. Sexual condition polygamous, autoicous, synoicous, dioicous. Seta elongate, red to reddish-yellow; smooth or papillose-scabrous to spinose distally. Capsule  inclined to pendulous, less frequently erect, ovoid to oblong-cylindric, symmetric, smooth, annulus none or weakly differentiated; peristome double, dark red or red-brown, of 16 teeth lanceolate to lance-subulate, furrowed, cross-striolate basally, papillose distally, trabeculate, sometimes bordered; endostome yellow to yellow-brown, finely papillose to nearly smooth, basal membrane generally high, keeled, segments lanceolate, about as long as the teeth; cilia absent; operculum long-rostrate to subulate from a conic base. Calyptra conic-mitrate to mitrate-campanulate, shortly lobed or deeply fringed-laciniate at the base, smooth or papillose-scabrous distally, naked [in our species]. Spores smooth to very finely papillose.


Genera 21, species ca. 400 (3 genera, 3 species in the flora): pan- and subtropical.



The Pilotrichaceae are diverse and abundant in the humid tropic. The family is mainly Neotropical (W. Frey 2009).   Three species, representing different genera, have reached the flora area, where they occur mainly in the South.  The family as currently understood is characterized by a double costa, generally with a stem hyalodermis present, undifferentiated laminal alar region, and hairy calyptra. Leaves are generally complanate, with generally a differentiation between lateral and dorsal or ventral leaves, seta variously papillose to spinose. The recent, rapid and complex changes in the circumscription of the Pilotrichaceae are outlined by T. F. Vaz-Imbassahy and D. P. da Costa (2008). These authors also present a chart comparing this and related families, indicating how fluid and complex the taxonomy of the family and its relationship to the traditional Hookeriaceae has been.  Such reconsiderations of the family boundaries began rather recently with a revision by H. A. Miller (1971).  W. R. Buck (1998) suggested two central lines of evolution in the family by which genera may be organized based on the presence or absence of a differentiated outer layer of inflated stem cortical cells (a hyalodermis), compared to an outer cortical layer of relatively thick-walled cells. A pilose calyptra is characteristic of the Pilotrichaceae, but the calyptra is naked in the three species, one in each of the three genera, represented in the flora area. There is extensive floristic literature on the family, but little of relevance to the flora area. Critical literature associated with the pre-1971 concept of the Hookeriaceae in the flora area is that of Welch (1962, 1966, 1972). All representatives of the family are rare in the flora area.



SELECTED REFERENCES Allen, B. 2010. Moss Flora of Central America. Part 3. Anomodontaceae--Symphyodontaceae. St. Louis. Buck, W. R. 1998. Pleurocarpous Mosses of the West Indies. Memoirs of the New York Botanical Garden. Vol.82. Crum, H. A. and L. E. Anderson. 1981. Mosses of Eastern  North America. New York.  Frey, W., ed. 2009. Syllabus of Plant Families: A. Engler's Syllabus der Pflanzenfamilien. Part 3. Bryophytes and seedless Vascular Plants. Berlin. Gradstein, S. R., S. P. Churchill, and N. Salazar-Allen. 2001. Guide to the Bryophytes of Tropical America. Mem. New York Bot. Gard. 86: 1--577. Miller, H. A. 1971. An overview of the Hookeriales. Phytologia 21: 243--252.  Reese, W. D. 1984. Mosses of the Gulf South. Baton Rouge and London. Vaz-Imbassahy. 2009. New combinations and new synonyms in Pilotrichaceae (Bryophyta) II. Nova Hedwigia 88: 465--474. Welch, W. H. 1962. The Hookeriaceae of the United States and Canada. Bryologist 65: 1--24. Welch, W. H. 1966. The Hookeriaceae of Mexico. Bryologist 69:1--68. Welch, W. H. 1972. Hookeriaceae: North America and West Indies, Additions and appendix. Bryologist  75: 456--461.


1. Laminal cells with a central papilla; leaf apex rounded-truncate and short-apiculate; seta papillose; stem hyalodermis absent, leaf border absent . . .  3. Callicostella, p. xxx.

1. Laminal cells smooth; leaf apex short to long-acuminate; seta smooth; stem hyalodermis present or absent; leaf border present or absent.

2. Leaf apex shortly acuminate, entire: laminal margins bordered by one row of linear cells, median cells large, nearly isodiametric, laxly hexagonal or oblong-hexagonal; stem hyalodermis present . . . 1. Cyclodictyon, p. xxx

2. Leaf apex long and slenderly pointed, serrate; laminal margins not bordered, median cells narrow, linear,  not noticeably lax; stem hyalodermis absent . . . 2. Trachyxiphium, p. xxx


1. CYCLODICTYON Mitten, J. Proc. Linn. Soc., Bot. 7: 163. 1863 * [Greek cyclos-, circular, and dictyon, network, alluding to large, nearly circular laminal cells]


Plants small and slender to medium-sized, soft, delicate, in white to pale green or bluish glaucous, thin and flattened mats. Stems and branches prostrate and rooting along the stem, irregularly to pinnately branched; with a hyalodermis 1-stratose over firm-walled median cells surrounding large thin-walled central cylinder; sparsely radiculose. Leaves  asymmetric, complanate, shriveled or more or less crisped when dry, broadly oblong or oblong-ovate, abruptly narrowing to a short or fairly long acumen, rarely ovate-lanceolate and gradually acuminate, dorsiventral and lateral leaves not much differentiated in shape, margins plane or occasionally narrowly recurved, bordered by 1 to occasionally several rows of elongate and narrower cells, entire or serrulate distally, otherwise similar to the laminal cells; costa double, divergent, extending about 2/3--3/4 the leaf length, ending beyond the leaf middle, smooth or somewhat serrulate distally; laminal cells hexagonal or oblong-hexagonal, lax, thin-walled,  transparent, smooth, becoming linear in 1 to few rows at the margins and forming a concolorous border, oblong or rhomboidal at leaf base. Specialized asexual reproduction not known. Sexual condition synoicous, dioicous or autoicous; perichaetial leaves small, ovate to lanceolate, short- to long-acuminate. Seta elongate, dark red, smooth. Capsule inclined to horizontal, oblong-cylindric, annulus narrow, operculum straight and long-rostrate from a conic base; exothecial cells not collenchymatous; peristome trabeculate. Calyptra mitrate, rostrate, short-lobed at the base, scarcely longer than the operculum, smooth.


Species 90 (1 in the flora): largely tropical and occasionally subtropical.


Cyclodictyon species occur largely in the Neotropics, though they are widespread in tropical Africa. Their habitat is moist to wet soil, humus, leaf litter, infrequently on rocks, occasionally epiphytic, from near sea level to 3900 m (S. R. Gradstein et al. 2001).


SELECTED REFERENCE: Gradstein, S. R., S. P. Churchill, and N. Salazar-Allen. 2001.

Guide to the Bryophytes of Tropical America. Mem. New York Bot. Gard. 86: 1--577.


1. Cyclodictyon varians (Sullivant) Kuntze, Revis. Gen. Pl. 2: 835. 1891  F


Hookeria varians Sullivant, Proc. Amer. Acad. Arts 5: 285. 1861


Plants in delicate, intricate  flat mats, with metallic, luster when dry. Stems much branched. Leaves   1.3--2 mm, ovate to broadly ovate, with short acumination,  marginal border of a single row of narrow, thin-walled and elongate cells; median cells 29-40 \um wide, 1.5--2:1, lax, oblong-hexagonal; costa divergent, slender,  ending only in the base of acumen, essentially smooth, without dorsal projections. Specialized asexual reproduction unknown. Sexual condition polygamous: synoicous and autoicous.  Seta 11--15.5 mm, somewhat sinuose. Capsule inclined, horizontal to pendulous, more or less asymmetric, contracted below the mouth when dry; operculum long and slenderly rostrate. Calyptra naked, lobed at base.


Wet places, occasionally aquatic, soil, humus, leaf litter, occasionally soil over limestone and limy sandstone rocks, springs, hammocks, stream banks, limestone sinks, deep ravine bottoms in deeply shaded forests; near sea level; Fld., La.; West Indies; Central America; n South America; Atlantic Islands (Bermuda).


Cyclodictyon varians is rare in the flora, found in southeastern United States in several counties of Florida and Louisiana in Iberia Parish). The cells are large enough for their character to be readily identified using a dissecting microscope.  Hookeria acutifolia is also large and flaccid and pale green, and also has larger, lax laminal cells (visible with a hand lens), with an indistinct border of narrower cells. It is distinguished by its complete absence of costa, whereas the leaves of C. varians have two distinct costae and its border is well defined. Hookeria species are gradually acuminate whereas C. varians is abruptly acuminate. Callicostella pallida has no border of differentiated cells, and though also having two costae, they are strong (not weak), ending near the apex (not 1/2 to 2/3 before the apex), and the cells lumens are centrally 1-papillose. H. A. Crum and L. E. Anderson (1981) discuss the doubtful report of Cyclodictyon obliquicuspis (Müller Hal.) H. A. Crum & E. B. Bartram (= C. roridum (Hampe) Kuntze) in Florida, reported in a paper by W. H. Welch (1971).


SELECTED REFERENCES: Crum, H. A. and L. E. Anderson. 1981. Mosses of Eastern North America. New York.  Gradstein, S. R., S. P. Churchill, and N. Salazar-Allen. 2001.

Guide to the Bryophytes of Tropical America. Mem. New York Bot. Gard. 86: 1--577. Welch, W. H. 1971. The Hookeriaceae of Jamaica, Hispaniola, and Puerto Rico. Bryologist 74: 77--130. 



2. TRACHYXIPHIUM  W. R. Buck, Brittonia 39: 219. 1987  * [Greek trachy-, rough, and xiphion, sword, alluding to sword-shaped leaves marginally roughened by serrations]


Plants small, medium-sized to fairly large, in glossy, soft, dense, light to brownish or golden green to bluish-green mats. Stems prostrate and creeping, closely irregularly and freely branched, hyalodermis lacking, the cortical layer with small cells somewhat thicker walled than the larger, thin-walled central cells.   Leaves  slightly asymmetric, lateral leaves generally spreading, vertical leaves erect,  somewhat to occasionally clearly complanate, flaccid, somewhat flexuose with the margins plane, incurved when dry, infrequently asymmetric, sometimes secund or falcate-secund, lanceolate to ovate-lanceolate, the short and broad to long and slenderly pointed acumen serrate marginally; margins broadly or narrowly recurved on one side, sharply serrate, especially distally, with bifid, tumid teeth, entire below, marginal cells not differentiated into a border; costa double, slender and well developed, 1/2--2/3\x length of the leaf, ending at about the base of the acumen,  parallel to slightly divergent, distally toothed on the dorsal side; laminal cells homogeneous, long-rhomboidal  to linear, narrow, elongate, smooth or sometimes prorulose by projecting distal cell ends.  Specialized asexual reproduction none. Sexual condition polygamous: synoicous but may also have male and female gametoecia; perichaetial leaves subulate from a broader base. Seta elongate, reddish, thick, smooth. Capsule black, dark brown or red-brown, ovoid, erect, inclined  to pendent, contracted below the mouth when dry, smooth; annulus none; operculum obliquely and generally narrowly long-rostrate. Calyptra conic-mitrate, covering the distal portion of the urn, naked, fringed at the base, often split on one side, smooth or distally slightly scabrous.


Species 15 (1 in the flora): pantropical.


Ten species of Trachyxiphium occur in the Neotropics, growing on wet soil, rocks and logs in humid lowlands to mid elevations, occasionally upper montane forests, from near sea level to 3400 m (S. R. Gradstein et al. 2001).


SELECTED REFERENCE  Gradstein, S. R., S. P. Churchill and N. Salazar-Allen. 2001. Guide to the Bryophytes of Tropical America. Mem. New York Bot. Gard.. 86: 1--577.


1. Trachyxiphium hypnaceum (Müll. Hal.) W. R. Buck, Brittonia 39: 220. 1987   C F


Hookeria hypnacea Müll. Hal., Bot. Zeit. (Berlin) 14: 421. 1856; Hookeriopsis heteroica Cardot; Trachyxiphium heteroicum (Cardot) W. R. Buck


Plants slender, flaccid, pale whitish yellow to brownish green to yellow-green, nearly hyaline when wet, not particularly complanate. Leaves  0.9--1.5 mm, somewhat distant (green or red stems visible between the leaf bases especially when dry), loosely erect-spreading, ovate- to narrowly lanceolate, becoming lightly to strongly falcate-secund near the stem tips, not undulate or plicate, somewhat flexuose but not crisped when dry, concave in proximal 2/3, distally gradually or sometimes abruptly narrowing to a long, flat, broad or slender and sharply pointed acumen that is somewhat flexuose when dry; margins serrulate in distal 1/3, tumid teeth single or double often tipped with a papilla; costa slender, cristate distally, dorsally strongly serrulate distally; distal laminal cells 7.5--10:1, linear-rhomboidal, pellucid with thin walls, smooth, the cell apices mostly pointed and often sharply prorulose. Seta orange-brown, smooth, 6.5--12 mm. Capsule black on a red seta, 0.7--1.5 mm. Spores spherical, 8--10.5 \um, essentially smooth.


Capsules mature early March. Rocks, wet places on soil, tree bases, wet, rotted wood, near spring seepage and stream banks, deep shade in wet forests, concrete culvert around a spring, cut-over  woods of Pinus, Fagus, Magnolia grandiflora; moderate elevations; La., Miss.; Mexico; Central America (Costa Rica in Cocos Island); South America.


Both the Louisiana and Mississippi specimens of Trachyxiphium hypnacea were reported as abundantly fruiting (W. D. Reese 1974). This taxon is rare in the flora area, occurring in one parish (Washington) in Louisiana and two counties (Franklin and Washington) in Mississippi. In Mexico it is known from Chiapas, Oaxaca, Puebla and Veracruz (C. Delgadillo M., personal communication). It is easily recognized by the erect-spreading, distally secund leaves, which are lanceolate-acuminate with smooth and narrow cells, and the dorsally strongly serrulate costae. Callicostella pallida is similar in the somewhat thinner but similarly robust double costa and broad leaves lacking a margin of differentiated cells, but the leaves are lingulate with an abrupt apiculus (not long-acuminate), laminal cells not smooth but with a central papilla, and isodiametric with firm walls (not linear-rhomboidal and thin-walled). The spores are small for the genus. W. D. Reese and B. E. Lemmon (1970) suggested the isolated occurrence of species of Pilotrichaceae “in sites well removed from their main area of distribution, is probably best regarded as the result of chance introduction, by hurricanes, of spores or other disseminules.” W. D. Reese (1974) noted that “both collections are associated with human activity: the man-made lake in Mississippi and the concrete culvert in Louisiana.”


SELECTED REFERENCES  Reese, W. D. and B. E. Lemmon. 1970. Mosses of Clear Springs Recreation Area, Homochitto National Forest, Mississippi. Castanea 35: 308--313. Reese, W. D. 1974. Notes on Louisiana mosses---VI. Bryologist 77: 467--468.   



3. CALLICOSTELLA (Müller Hal.) Mitten, J. Proc. Linn. Soc., Bot. Suppl. 1: 136. 1859, conserved name * [Latin calli, hardened or thick, and costa, rib, alluding to the strong costae]


Hookeria sect. Callicostella Müller Hal., Syn. Musc. Frond. 2: 216. 1851; Hookeria subg. Callicostella (Müller Hal.) Hampe; Schizomitrium Bruch & Schimp. in Bruch, Schimper & Gümbel, rejected name.


Plants small to medium-sized, in dull, sordid pale-green, yellowish, brownish, sometimes bluish-green, flattened mats. Stems prostrate and rooting, branching freely, regularly or irregularly pinnate; hyalodermis lacking, epidermis composed of small, thick-walled cells, central cylinder of large, thin-walled cells, sparsely radiculose in tufts. Leaves somewhat asymmetric, more or less complanate, shriveled, often crisped when dry; ovate-oblong to lingulate, dimorphic, ventral leaves often more acuminate, dorsal and lateral leaves mostly broadly oblong to oblong-ovate, apex bluntly and broadly rounded, usually abruptly apiculate, margins plane, not or obscurely bordered,

crenulate to serrulate to strongly toothed in the apical quarter, smooth in basal quarter; costa double, strong, ending in the leaf apex, subpercurrent, divergent from the base, parallel or somewhat convergent distally, distally toothed dorsally; laminal cells isodiametric or a little longer than wide, irregularly hexagonal to quadrate, variously short-rectangular and thin-walled in the proximal half to nearly isodiametric in the distal half with thicker walls and rounder corners; each  lumen  with a single, central sharp papilla on both surfaces, laminal cell corners angular, not thickened; basal cells rectangular, 6--2:1; smooth, cell walls thin, even, somewhat vesiculose at mid-base, small alar group turning inward in a curve at the extreme basal margin. Specialized asexual reproduction rare, of brownish, 1-seriate, papillose gemmae in the axils of the leaf.

Sexual condition polygamous, infrequently dioicous; perichaetial leaves small, inconspicuous, ovate- or linear-lanceolate, gradually acuminate to acute, with costa double. Seta red to reddish yellow, smooth or distally papillose, sometimes strongly so, or scabrous throughout. Capsule ovoid or oblong-cylindric, inclined to horizontal to pendulous, exothecial cells mostly collenchymatous, annulus none; operculum abruptly short-rostrate or subulate; peristome with well-developed trabeculae ventrally, projecting from the sides. Calyptra narrowed and shortly or deeply lobed at the base, mitrate-campanulate, smooth or sometimes split on one side from base, somewhat scabrous or with a few hairs distally.


Species 95 (1 in the flora): pantropical and southern South America.


Callicostella is characterized by broad, lingulate, shortly and abruptly acuminate leaves with no border. The long, tough double costa is distinctive, as are the small, isodiametric, firm-walled leaf-cells, especially those of the apex, each with a single, central papilla. The distal margins of the leaf are also strongly serrate with teeth often forking. Other species in the genus may have calyptra fimbriate at base, but our species the calyptra is only lobed. A technical character that helps to distinguish this genus from closely related genera is the epidermis of the stem section composed of small, thick-walled cells (i.e. lacking a hyalodermis).


SELECTED REFERENCES: Bowers, F. D. Callicostella. In:  A. J. Sharp, H. A. Crum and P. M. Eckel, eds. The Moss Flora of Mexico. Mem. New York Bot. Gard. 2: 789--792.  Buck, W. R. 1998. Pleurocarpous Mosses of the West Indies. Bronx, New York. Crosby, M. R. 1974. Toward a revised classification of the Hookeriaceae (Musci). J. Hattori Bot. Lab. 38: 129--141. Frey, W., ed. 2009. Syllabus of Plant Families: A. Engler's Syllabus der Pflanzenfamilien. Part 3. Bryophytes and Seedless Vascular Plants. Berlin. Gradstein, S. R., S. P. Churchill and N. Salazar-Allen. 2001. Guide to the Bryophytes of Tropical America. Mem. New York Bot. Gard.. 86: 1--577.


1. Callicostella pallida (Hornschuch) Ångström, Öfvers. Förh. Kongl. Svenska Vetensk.-Akad. 33(4): 27. 1876  F


Hookeria pallida Hornschuch in Martius, Fl. Bras., 1(2): 64. 1840; Schizomitrium pallidum (Hornschuch) H. A. Crum & L. E. Anderson


Leaves with distal laminal cells homogeneous, ca. 8--11 \um wide, not decurrent, differentiated lateral leaves more asymmetrical than the erect dorsal/ventral leaves, long cells from the stem may remain attached at the insertion. Specialized asexual reproduction not seen. Sexual condition polygamous (synoicous and autoicous, appearing to have some male or female buds that also contain both sex organs); perichaetial leaves ovate-lanceolate, 0.8--1 mm, gradually acuminate to acute. Seta 6--8(--20) mm, moderately to strongly scabrous throughout with broad, low papillae. Capsule ca. 1 mm, constricted below the mouth and at the short neck when dry; operculum 0.7--1 mm. Spores 8--11 \um. 


Capsules present winter (late December--March). Moist sites, sometimes subaquatic or submerged, usually moist rock and soil, occasionally rotted stumps, logs, limestone rocks in springs, wet limy muck, sandy soil, stream banks, water-filled ditches, hammocks, deeply shaded ravines, dark swampy subtropical forests with Magnolia and Illicium; may be associated with Cyclodictyon and Hygroamblystegium; low elevations near sea level, 0--80 m; Ala., Fld., La.; Mexico; Central America; West Indies; South America.


The presence of Callicostella pallida in the flora is apparently not relictual, but recently introduced (W. D. Reese 1984). Like Callicostella pallida, Trachyxyphium heteroicum has a robust double costa and broad leaves lacking a margin of differentiated cells, but T. heteroicum has leaves that are long-acuminate (not truncate-lingulate with an abrupt apiculus), cells smooth (with no central papilla), leaf cells linear-rhomboidal and thin-walled (not isodiametric with firm walls).