MBG: Research: NSF-PEET Project in Systematic Bryology

A revision of Pilotrichella (Lembophyllaceae: Musci). Part 1. Section Pilotrichella

Pilotrichella (C. Müll.) Besch. is a genus of predominantly epiphytic, frequently pendulous mosses of tropical and subtropical American-African distribution. Hedwig (1801) described the oldest species now placed in Pilotrichella (as Leskea flexilis Sw. ex Hedw.), but the species generally accepted in the genus were first brought together by Müller (1850) under Neckera Hedw. sect. Pseudopilotrichum. C. Müll. subsections Orthostichella C. Müll. and Pilotrichella C. Müll.

Bescherelle (1872) elevated Müller’s subsect. Pilotrichella to generic rank. The newly established Pilotrichella was broadly conceived and included four sections: Orthostichella (C. Müll.) Besch., Eupilotrichella (C. Müll.) Besch., Papillaria (C. Müll.) Besch., and Meteoridium (C. Müll.) Besch. Papillaria had previously been removed from this group by Lorentz (1864). Jaeger & Sauerbeck (1877) refined Pilotrichella by dividing it into two unranked groupings: Eupilotrichella (including Bescherelle’s sect. Meteoridium) and Orthostichella. Section Meteoridium was removed from Pilotrichella by Brotherus (1906) who also positioned the genus (with sections Orthostichella and Eupilotrichella) in the tribe Meteorieae. This placement of Pilotrichella was followed by Fleischer (1908) who first assigned the genus to the Meteoriaceae (tribe Pilotrichelleae). The association of Pilotrichella with the Meteoriaceae has been generally accepted (see e.g., Brotherus 1925, Bartram 1949, Florschütz 1964, Walther 1983, Vitt 1984, Spessard-Schueth 1994, Churchill & Linares 1995, Duarte-Bello 1997, Magill & van Rooy 1998, Gradstein et al. 2001).

The Meteoriaceae are usually placed in the Leucodontales (Fleischer 1908, Brotherus 1925, Walther 1983, Vitt 1984). The family, however, was transferred to the Hypnales by Buck (1994) and placed near the Brachytheciaceae in part because its exostome teeth are often horizontally striate at base and it lacks stolon-like primary stems that are tightly adherent to the substrate as well as greatly reduced stolon leaves. Buck (1994, 1994a) also reconsidered Pilotrichella and its systematic placement. As a result Orthostichella C. Mull. was resurrected as a genus (as Pseudopilotrichum (C. Müll.) Buck & Allen) and both genera along with Weymouthia Broth. and Squamidium (C. Müll.) Broth. transferred to the Lembophyllaceae.

There are a number of tropical and subtropical pleurocarpous genera found predominately in epiphytic/pendulous habitats. These genera present classification problems because they appear to represent several phylogenetic lines as judged by their very different peristomial forms, but they exhibit considerable convergence in their gametophytic features. Pilotrichella is one of these problematic genera. It is difficult to decide if it belongs in the Meteoriaceae or Lembophyllaceae because its reduced peristome shows affinities to both families and it is hard to determine whether its gametophytic features are indicative of propinquity of descent or convergence. This situation is further complicated because the Meteoriaceae and Lembophyllaceae are so similar (e.g., compare the family descriptions of the Lembophyllaceae and Meteoriaceae in Buck & Goffinet 2000).

The leaves and stems of most genera placed in the Meteoriaceae often have an intense black coloration. This odd feature is usually only noticed in passing, but it is so distinctive that when present one can immediately assigned an unknown to the Meteoriaceae. Genera placed in the Lembophyllaceae can be green, yellowish red or brown, but they never exhibit an intense black color. Furthermore, all of the genera now placed in the Meteoriaceae that can produce this intense black coloration also have single costae. On the basis of these two features it appears that Squamidium should be returned to the Meteoriaceae. Pilotrichella, Orthostichella, and Weymouthia which are ecostate or have short double costae and a green, yellowish red or brown coloration seem properly placed in the Lembophyllaceae. Within the Lembophyllaceae Pilotrichella appears isolated by virtue of its lack of a stem central strand, absolutely ecostate leaves, and more reduced peristome.

As noted above Orthostichella is generally considered a section of Pilotrichella, but Müller (1879) used the name at the generic level as did Buck (1994, 1994a). Orthostichella differs significantly from Pilotrichella in its smaller plant size, and in often having primary stolons as well as stipitate stems. It also differs from Pilotrichella in having spirally ranked leaves with sparsely developed alar cells, and often its leaves have short double costae. Sporophytically Orthostichella differs from Pilotrichella in having shorter setae and smooth to papillose exostome teeth. Additionally the presence of large spores (to 64 μm) in Pilotrichella as another feature that distinguished the two taxa. For these reason Orthostichella is here considered distinct from Pilotrichella at the generic level.

Pilotrichella is stable in most of its features. Its stolons, stems, and branches are identical in structure. It lacks a stem central strand, and its axillary hairs are usually reddish throughout. When the reddish coloration in the axillary hairs is weakly expressed it is the upper rather than the basal cells that are remain colored. The stem and branch leaves of Pilotrichella are monomorphic, strongly concave, variously ovate in shape, and always lack a costa. Its leaf margins are generally broadly incurved and entire to serrulate, and its linear-flexuose leaf cells are often strongly porose. The alar cells in Pilotrichella are a distinctive feature of the genus. They are well-developed and occur as excavate groups of reddish-yellow, subquadrate to rectangular, porose cells. Gametophytic feature of Pilotrichella that show significant variation include:1. relative plant size; 2. branch bud shape; 3. leaf shape; 4. leaf margin stance; 5. extent of alar cell differentiation; 6. leaf apex shape; and 7. spore size.

The sporophytes of Pilotrichella are uniform throughout the genus. The setae are elongate and variously papillose roughened. The genus has ovoid to short-cylindrical capsules, long-rostrate opercula, and hairy, cucullate calyptrae. The Pilotrichella peristome is diplolepideous and reduced with yellowish white exostomes and endostomes that are nearly the same length. The more or less linear exostome teeth are lightly horizontally striate on the dorsal (outer) surface at base. The endostome has a low basal membrane with filamentous, narrowly perforated segments, and cilia are usually absent. Even though the peristome is significantly reduced, the presence at the base of the exostome teeth of horizontal striae seems to indicate the peristome is basically hypnoid.

The name Pilotrichella combines the generic name Pilotrichum with the Latin substantival suffix -ella (diminutive).

Pilotrichella (C. Müll.) Besch., Mém. Soc. Sci. Nat. Cherbourg 16: 222. 1872.

Neckera subsect. Pilotrichella Syn. 2: 129. 1850. Lectotype (designated here): Leskea flexilis Sw. ex Hedw.

Pilotrichella sect. Turgidella C. Müll., Flora 82: 464. 1896, invalid name, no description. Type: Meteorium mauiensis Sull.

Pilotrichella sect. Gastrella C. Müll., Flora 82: 464. 1896, invalid name, no description. Type: Pilotrichella desmoclada C. Müll.

Pilotrichella sect. Eupilotrichella Besch. ex Broth., Nat. Pflanzenfam. 1(3): 811. 1906, illegitimate name (Art. 21.3, Greuter 2000).

Plants small, medium-sized or robust, dull, light green, green, yellow-green, reddish yellow, or golden brown, in loose or stiff mats, often with pendent strands. Stem and branches in cross section with sclerodermis, firm-walled cortical cells, central strand absent; paraphyllia absent; pseudoparaphyllia absent, scale leaves present over branch buds. Primary stems creeping; rhizoids generally on the parts of the stems that touch the substrate, in circular clusters abaxially to the leaf insertions, dark red, smooth to finely roughened, not or sparsely and irregularly branched; leaves smaller but not different in form or structure from secondary stem and branch leaves. Secondary stems arising irregularly from the primary stems, or primary stems transformed at the tips into secondary stems, often pendent, irregularly branched; axillary hairs numerous, all cells reddish, basal cells short, subquadrate, upper cells long cylindrical; rhizoids absent. Secondary stem and branch buds short and swollen or narrowly elongate and terete. Leaves not ranked, turgid when dry, erect-spreading, spreading or wide-spreading when wet, concave, ovate, oblong-ovate, obovate, or ovate-deltoid, at times panduriform, somewhat clasping at base and variously auriculate; apices broadly rounded, acute or acuminate, mucronate, acuminate, cuspidate or hair-pointed, leaf tips reflexed or straight; margins broadly incurved above, at times meeting or overlapping near the apex, entire below, variously serrulate directly below the apex; costa absent; leaf cells linear-flexuose, consistently porose at base, porose or occasionally smooth above, alar cells strongly differentiated in bulging, excavate groups, subquadrate to short rectangular, usually dark red or reddish orange. Branch and stem tips occasionally flagelliform, plants sometimes with slender branchlets having microphyllous leaves, or short branches with deciduous leaves. Dioicous. Perigonia gemmate, lateral on secondary stems and branches, outer perigonial leaves clasping at base, squarrose recurved above, inner perigonia leaves broadly ovate, orange-red across the base; paraphyses and curved-cylindrical antheridia numerous. Perichaetia on short lateral branches; paraphyses and archegonia numerous; outer leaves clasping below, squarrose above, inner leaves sheathing, oblong-lanceolate, long acuminate; vaginula of fertilized perichaetia densely hairy. Setae elongate, red, smooth below and papillose above or papillose roughened throughout. Capsules exserted, erect, ovoid to short cylindrical; exothecial cells subquadrate to irregularly subrectangular, firm walled; stomata superficial in neck; opercula long rostrate; annuli rudimentary; peristome diplolepideous, yellowish white, exostome on dorsal (outer) surface lightly horizontally striate at base, finely papillose above, trabeculae weakly developed on both sides, endostome nearly as long as exostome, basal membrane low, segments filamentous, narrowly perforated, papillose, cilia rudimentary or absent. Calyptrae cucullate, densely hairy. Spores lightly roughened, oblong to rounded-triangular, 34–64 μm long or round, 18–28 μm long.

1. Leaves ovate-deltoid, long cuspidate to piliferous; branch buds narrow, elongate, and terete 1. P. cuspidans

1. Leaves oblong-ovate to broadly ovate, mucronate to cuspidate; branch buds short and swollen ......... 2

2. Plants with slender branchlets having microphyllous leaves, flagelliform branch tips, or deciduous leaves 3

2. Plants lacking slender branchlets, flagelliform branches absent, leaves firm and nondeciduous 5

3. Leaf alar cells extensively developed, not restricted to an excavate group in the auriculate angle 5. P. reesei

3. Leaf alar cells moderately developed, more or less restricted to an excavate group in the auriculate angle 4

4. Near all leaf apices erect, generally cuspidate to long cuspidate; flagelliform branch tips and/or deciduous leaves present 4. P. mauiensis

4. Most leaf apices reflexed, mucronate; only deciduous leaves present

2a. P. flexilis form nudiramulosa

5. Leaf alar cells extensively developed, not restricted to an excavate group in the auriculate angle 5. P. reesei

5. Leaf alar cells moderately developed, more or less restricted to an excavate group in the auriculate angle 6

6. Near all leaf apices erect, generally cuspidate to long cuspidate 4. P. mauiensis

6. Most leaf apices reflexed, obtuse, broadly acute, mucronate or apiculate........ 7

7. Plants medium-sized to robust, leaves 1.7–3.0 mm long . 2. P. flexilis

7. Plants small to medium-sized, leaves 1.2–1.6 mm long... 8

8. Branch leaves turgid when dry; leaves often cochleariform, obtuse, mucronate apices; shortly incurved, upper leaf margins never overlapping and only occasionally approaching each other below the apex 6. P. vermiformis

8. Branch leaves erect to erect-spreading when dry; leaves oblong-ovate, broadly acute, broadly incurved upper leaf margins usually overlapping below the apex 3. P. mascarenica

1. Pilotrichella cuspidans Ren. & Card., Bull. Soc. Roy. Bot. Belgique 29(1): 180. 1890. Protologue: Haiti. Haïti, Port au Prince, ad truncos arborum (Bertrand). Holotype: Haiti: Port au Prince, Leg. Bertrand, Herb. J. Cardot (PC). Isotypes: Haiti, Leg. R[ev]. P. Bertrand, Herb. J. Cardot (H); Haiti, leg. Rev. Bertrand, Herb. R. Renauld (H); Haiti leg. R[ev]. P. Bertrand com. Brotherus, Herb. J. Cardot (S); Haiti. Leg. R[ev]. P. Bertrand, 1888, Herb. J. Cardot (NY); Port-au-Prince, Haiti, Leg. Rev. R. P. Bertrand, 1888, ex Herbarium of the New York Botanical Garden (FH).

Renauldia subpilifera Williams, J. Wash. Acad. Sci. 20: 176. 1930. Protologue: Dominican Republic. Dominican Republic: Polo, Prov. de Barahona, 600-1200 meters, Feb. 26–March 12, 1922 (Abbot 1879c). Holotype: Dominican Republic. Dominican Republic: Prov. de Barahona, Loma la Haut, Polo, Altitude 600–1300 m or less, Feb. 26–Mr. 12, 1922. W. L. Abbot 1879c (NY); Isotype: Dominican Republic. Loma la Haut, Polo 600–1300 m., Feb. 26–Mr. 12, 1929 [sic]. W. L. Abbot 1879c. (FH).

Nomenclatural notes.

1. The protologue of P. cuspidans does not indicate when the type material was gathered, and most type material likewise gives no collection date. There are, however, several Bertrand collections of P. cuspidans in FH, PC, and NY dated either 1887 or 1888. The material in PC and NY collected in 1887 is not marked as type material, while a collection in NY from Cardot’s herbarium marked “sp. nov.” is dated 1888. The “1888” collection is identical to the holotype.

Plants medium-sized to robust, dull, light green yellow-green, reddish yellow, or golden brown, in stiff mats often with pendent strands. Primary stems yellow-red, creeping, in cross section with sclerodermis of 4–6 thick-walled cells, cortical cells firm-walled, hyaline to yellow, central strand absent; rhizoids sparse, in circular clusters abaxially to the leaf insertions, dark red, smooth to finely roughened, not or sparsely and irregularly branched. Leaves reduced, erect to appressed, broadly triangular to broadly ovate, auriculate at base, 0.9–1.5 mm long, acuminate, hair-pointed; leaf cells linear-flexuose, thick-walled, porose, alar cells dark red, subquadrate to short-rectangular, upper margins serrulate. Secondary stems horizontal, erect or pendent, to 15 cm long, irregularly branched, arrested branch primordia numerous, in cross section with sclerodermis of 4–5 small, thick-walled, reddish orange cells, cortex cells enlarged, firm-walled, pale yellow, central strand absent; axillary hairs 3–6 cells long, reddish throughout, basal cells 1–2, short, quadrate to subquadrate, upper cells 2–3, long-cylindrical; rhizoids absent. Secondary stem and branch apices narrowly elongate and terete; leaves ovate-deltoid to broadly ovate, not ranked, wide-spreading to erect-spreading from the base, margins incurved when dry, erect to erect-spreading when wet, 2–3 mm long, concave, clasping at base, auriculate, apex acuminate, long-cuspidate to hair-pointed, leaf tips straight; margins broadly incurved, entire below, serrulate below the apex; costa absent; leaf cells linear-flexuose, porose throughout, median cells 30–60 x 4–6 μm, basal cells shorter and broader, alar cells bulging in excavate groups, subquadrate to short-rectangular, 14–30 x 10–14 μm, yellow-red, reddish orange or red. Dioicous. Perigonia gemmate, lateral on secondary stems and branches, 1.0–1.3 mm long, outer perigonial leaves clasping at base, squarrose recurved above, 0.8–1.0 mm long, inner perigonial leaves broadly ovate below, long-acuminate above, orange-red across the base, cells elongate-flexuose, porose throughout, costa absent; paraphyses and curved-cylindrical antheridia numerous. Perichaetia terminal on short lateral branches, unfertilized perichaetia to 2 mm long; paraphyses and archegonia numerous; leaves clasping below, squarrose above; fertilized perichaetia with hairy vaginula; leaves sheathing, outer leaves to 2.0 mm long, inner leaves oblong-lanceolate, long-acuminate, 3 mm long; ecostate, laminal cells long-linear and porose. Setae elongate, 6–8 mm long, smooth to lightly roughened below, papillose above, red to reddish yellow. Capsules exserted, erect, ovoid to short cylindrical, 1.8–2.0 mm long; exothecial cells subquadrate to irregularly short-rectangular, firm-walled; stomata superficial in neck; opercula long rostrate, 1.6–2.0 mm long; annuli rudimentary; peristome diplolepideous, yellowish white, exostome to 508 μm long, dorsal (outer) surface lightly horizontally striate at base, finely papillose above, trabeculae weakly developed on both sides, endostome nearly as long as exostome, basal membrane low, segments filamentous, narrowly perforated, papillose, cilia rudimentary or absent. Mature calyptra not seen, immature calyptra cucullate, hairy. Spores round, lightly roughened, 18–22 μm long.

Etymology. The specific epithet cuspidans is a Latin active present participle meaning “pointed” and refers to its long, terete stem and branch buds.

Distribution. Caribbean (Cuba, Haiti, Dominican Republic).

Illustrations. Williams (1930, Fig. A 7–10); Duarte-Bello (1997, Pl. 201); Buck (1998, Pl. 90 7–12). Figures 1 & 2.

Figure 1. Pilotrichella cuspidans. A. Leaf apex. B & C. Branch and stem leaves. D. Upper leaf margin. E. Median leaf cells. F & G. Primary stem leaves. H. Alar cells.

Scale in mm: bar = 0.06 (A, D, E, H); bar = 0.5 (B, C, F, G). Figures A–E, H from Duncan 28; figures F & G from Zanoni 30375.

Figure 2. Pilotrichella cuspidans. A. Habit. B. Exostome tooth, dorsal (outer) surface. C. Endostome segment and part of basal membrane, ventral (inner) surface. D. Capsule and operculum. E. Stem cross section. Pilotrichella flexilis form nudiramulosa. F. Habit. Scale in mm: bar = 0.08 (B, C, E); bar = 0.6 (D); bar = 3.3 (A); bar = 5.1 (F). Figure A from Steere 22825; figures B–D from Buck 8304B; figure E from Bolay 92; figure E from the type; F from the type.

Ecology. Over limestone along road banks and in forest, tree trunks and branches, pendent from branches, twigs, and rotten logs; 1158–1940 m.

Selected specimens examined. CUBA. Santiago de Cuba: Clement (S). HAITI. Ouest: Imshaug 22806 (NY); Sud: Duncan 53a (MO); Sud’est: Buck 9453 (NY). DOMINICAN REPUBLIC. Barahona: Steere 22825 (H, NY); Independencia: Buck 14639 (B, NY); La Estrelleta: Buck 4573 (NY); La Vega: Norris et al. 4999 (NY); Pedernales: Steere 22907 (H, NY).

Pilotrichella cuspidans generally has long terete apical buds, variously deltoid stem leaves, and long cuspidate to hair-pointed leaves. Although seta length is a variable feature of most Pilotrichella species, those of P. cuspidans are consistently short, never longer than 9 mm. Most other members of the genus have massive irregularly shaped spores, but in P. cuspidans they are small (18–21 μm) and more or less round. The majority of P. cuspidans collections are unmistakable because they have hair-pointed stem and branch leaves. Collections with cuspidate stem and branch leaves, however, can be difficult to separate from P. reesei. The shape and length of the apical buds in P. cuspidans is the best diagnostic feature of the species. These apical buds are exceptionally long and smoothly julaceous, no other species of Pilotrichella has this feature.

Pilotrichella flexilis has short, swollen apical buds and further differs from P. cuspidans in having broad, oblong-ovate stem leaves with short mucros that are mostly recurved. Although the alar cells in P. cuspidans and P. flexilis are similar in color, those of P. cuspidans are more extensively developed than those of P. flexilis. Plants in some collections of P. cuspidans are noticeably smaller than those of P. flexilis, but P. cuspidans is so variable in size that this feature can not be used alone to separate the two species. The setae in P. cuspidans are generally smaller than those of P. flexilis which typically have setae greater than 10 mm long. In both species exostome ornamentation and endostome development are the same.

There are some collections of P. cuspidans with relatively short leaf apices and weakly developed apical buds (see e.g., Allard 17620 NY) that are difficult to distinguish from P. mauiensis. The presence in P. mauiensis of more broadly ovate leaves with less developed alar cells that are restricted to the moderately developed auriculate-angle will serve to distinguish it from all collections of P. cuspidans.

Pilotrichella reesei is especially difficult to distinguish from P. cuspidans because it has somewhat attenuate stem apical buds, distinctly auriculate leaves, and similar alar cell development. In P. reesei , however, the branch apical buds are short and swollen, flagelliform branches sometimes occur, and its leaves are short cuspidate (identical to those of P. mauiensis) to mucronate. Furthermore, while most of its leaf apices are erect, occasionally the leaves have recurved mucros (identical to those of P. flexilis).

2. Pilotrichella flexilis (Hedw.) Ångstr., Kongl. Svenska Vetensk. Acad. Handl. 33(11): 34. 1876. Leskea flexilis Sw. ex Hedw., Sp. Musc. Frond. 234. 1801. Hypnum flexile (Hedw.) Sw. in Brid., Muscol. Recent. 2(2): 153. 1801. Hookeria flexilis (Hedw.) Sm., Trans. Linn. Soc. London 9: 281. 1808. Isothecium flexile (Hedw.) Brid., Bryol. Univ. 2: 361. 1827. Neckera flexilis (Hedw.) C. Müll., Syn. Musc. Frond. 2: 129. 1850. Meteorium flexile (Hedw.) Mitt., J. Linn. Soc., Bot. 12: 438. 1869. Pilotrichum flexile (Hedw.) C. Müll. in Par. Index. Bryol. (ed. 2). 4: 4. 1905. Protologue: Jamaica. Jamaica et insulae australes [Swartz]. Holotype: Leskea flexilis Spec. Musc. 234. Tab. 96. Hypnum flexile Swartz Prod. p. 141 (G) Isotypes: Hypnum flexile Swz. N° 2069, Herbarium Swartz (S); Jamaica, Swartz (H); a celeb D. D. Ol. Swartz. Jamaica (S); Leskea flexilis fl. ind. occ. from D. Swartz, Herb. Hooker, H. 2592 (BM).

Pilotrichum cochlearifolium C. Müll., Linnaea 43: 599. 1843. Neckera cochlearifolia (C. Müll.) C. Müll., Syn. Musc. Frond. 2: 130. 1850. Pilotrichella cochlearifolia (C. Müll.) Besch., Mem. Soc. Sci. Nat. Cherbourg 16: 223. 1872. Meteorium cochlearifolium Mitt. ex Par., Index Bryol. (ed. 2) 4: 2. 1905. Protologue: Mexico. Habitat in regno Mexicano, ubi legit Cl. C. Ehrenberg. Lectotype: Mexico: leg. C. Ehrenberg (JE, designated here). Isolectotypes: Mexico leg. C. Ehrenberg (H, S).

Neckera turgescens C. Müll., Syn. Musc. Frond. 2: 131. 1850. Meteorium turgescens (C. Müll.) Mitt., J. Linn. Soc., Bot. 12: 440. 1869. Pilotrichella turgescens (C. Müll.) Besch., Mém. Soc. Sci. Nat. Cherbourg 16. 223. 1872. Protologue: Mexico. Mexico: C. Ehrenberg. Lectotype: Mexico. Erhenberg. Muller in Hb. Hook. (BM). Isolectotypes: Mexico. Erhenberg. Muller in Hb. Hook. (H, NY); Mexico: C. Ehrenberg (S).

Meteorium orbifolium Mitt., J. Linn. Soc., Bot. 12: 440. 1869, illegitimate name, protologue includes an earlier name in synonymy. Protologue: Mexico and Taboga. Mexico, Ehrenberg; ins. Taboga, Seemann. Lectotype. Mexico: leg. C. Ehrenberg (JE, designated here). Isolectotypes: Mexico leg. C. Ehrenberg (H, S).

Pilotrichella recurvo-mucronata C. Müll., Bull. Herb. Boiss. 5: 563. 1897. Protologue: Guadeloupe and Puerto Rico. Guadeloupe: L’Herminier: Puerto Rico, prope Uticado, in sylva primaeva: Sintensis 10. III. 1889. Lectotype: Guadeloupe: L’Herminier (BM, designated here). Isolectotypes: Guadeloupe: L’Herminier (H, FH, NY, S).

Pilotrichella eroso-mucronata C. Müll., Bull. Herb. Boiss. 5: 563. 1897. Protologue: Jamaica. Jamaica, New Haven Pass, inter Capressinam arcuatipedem: W. Fawcett, 1896. Type not seen, synonymized by Britton (1913).

Pilotrichella squarrulosa C. Müll. in Broth., Acta Soc. Sci. Fenn. 19(5): 24. 1891. Protologue: Brazil. Prov. Minas Geraës, Caraça; sterilis [E. Wainio]. Lectotype: Brasilia, prov. Minas Geraes, Caraça 1885. leg. E. Wainio (H, designated here). Isolectotypes: Brasilia, Minas Geraës, Caraça 1885 leg. E. Wainio, comm. Brotherus (BM, PC).

Pilotrichella pallidicaulis C. Müll., Bull. Herb. Boissier 6(2): 117. 1898. Protologue: Brazil. Brasilia, Sa. Catharina, Serra Geral, in araucarieto ad truncos arborum, Januario 1891 c.fr. parcissimis vetustis atque junioribus: E. Ule, Coll. 1164; Minas Geraës, Serra Italiaia, 2000 m. alta, ad arbores sylvestres, Febr. 1894; sterilis: idem, Coll. N° 1844. Lectotype: Brasilia, Serra do Itatiaia, an Baümen im Walde 2000 m., 2/1894, leg. E. Ule 1844 (H, designated here).

Pilotrichella araucarieti C. Müll., Hedwigia 40: 85. 1901. Protologue: Brazil. Brasilia, Sa. Catharina, Serra Geral, in truncis arborum araucarieti, Januario, Martio et Majo 1890 et 1891: E. Ule, Coll. L, M. No. 873, 874, 1022. Lectotype: Brasilia, prov. S. Catharina, Serra Geral, an Baümstaminen in Araucarienwalde, Maji 1890, leg. E. Ule 873 (H. designated here). Syntype: E. Ule 874 (H).

Pilotrichella araucarieti var. crassicaulis C. Müll., Hedwigia 40: 85. 1901. Protologue: Brazil. In iisdem locis: idem, Coll. No. [Ule] 868; Minas Geraës, Serra Itabira, in truncis arborum sylvestrium, Febr. 1892: E. Ule, Coll. No. 1459 sub Pil. squarruloso C. M.; Serra Caraça: E. Wainio (1885) in Hb. Brotheri; Rio de Janeiro, Mte. Tijuca, Oct. 1893: E. Ule, Coll. No. 1688, 1689 sub Piltr. sediramea C. M.; Petropolis, in pseudobulbis Orchidearum: Hb. Döring 1862. Lectotype: Brasilia, prov. S. Catharina, Serra Geral, an Baumstammen im Araucarienwalde, Maji 1890, leg. E. Ule 868 (H, designated here). Syntypes: Brasilia, Minas Geraës, Serra Iteolomy [?], auf Baumstammen in Waldehen, Febr. 1892. leg. E. Ule 1459 [under Pilotrichella squarrulosa C. M.], (H); Brasilia, prov. Minas Geraes, Caraça, 1885. leg. E. Wainio (H); Rio de Janeiro, auf Zweigen im Walde der Tijuca, 10/1893, leg. E. Ule 1688, 1689 (both H).

Pilotrichella sediramea C. Müll., Hedwigia 40: 85. 1901. Invalid name, lacking a description and mentioned in synonymy. Based on: [Brazil] Rio de Janeiro, Mte. Tijuca, Oct. 1893: E. Ule Coll. No. 1688, 1689 (both H).

Pilotrichella rigens Card., Rev. Bryol. 37: 8. 1910. Protologue: Mexico. Etat de Hidalgo: Honey-station, 1904 (Pringle, n. 15061). Holotype: Plantae Mexicanae. State of Hidalgo, Honey Station, 10 May 1904, C. G. Pringle 15061 (PC). Isotype. Plantae Mexicanae. State of Hidalgo, Near Honey Station, 10 May 1904, C. G. Pringle 15061 (NY).

Pilotrichella flexilis var. robusta Broth. in Thér., Mem. Soc. Cub. Hist. Nat. “Felipe Poey” 14: 360. 1940. Invalid name, no description given. Based on: Cuba, Sierra de Banao, Santa Clara (Léon 8,326) (NY).

Pilotrichella perrobusta P. de la Varde, Rev. Bryol. Lichénol. 19: 153. 1950. Protologue: Madagascar. Sommet oriental du massif de Marojéjy (N.E.) à l’ouest de la haute Manantenina, affluent de la Lokoho. Gneiss et quartzite. Alt. 1,850–2,100 m. [H. Humbert]. Holotype: Madagascar. Sommet oriental du massif de Marojéjy (Nord-Est) à l’ouest de la haute Manantenina, affluent de la Lokoho. Gneiss et quartzite. Altitude. 1850–2137 m. Date de la récolte: 26 Mars–2 Avril 1949. Leg. H. Humbert & G. Cours (PC).

Pterobryopsis subcochlearifolia Thér. in Crum & Arzeni, Rev. Bryol. Lichénol. 22: 155. 1953. Invalid name, lacking a description and mentioned in synonymy. Based on: Panamá, s.l., Bro Hélion, 1906 (H).

Nomenclatural notes.

1. A syntype (Serra Caraça: E. Wainio (1885) in Hb. Brotheri) of Pilotrichella araucarieti var. crassicaulis, described in 1901, is also the type (Brazil. Prov. Minas Geraës, Caraça; sterilis [E. Wainio]) of Pilotrichella squarrulosa, described in 1891.

2. Wijk et al. (1967) considered P. araucarieti an illegitimate name because its syntypes included a species (P. squarrosa) of earlier priority. The questionable syntype, however, is not the type of P. squarrosa, but only a collection that had previously been named P. squarrosa.

Plants medium-sized to robust, dull, light green, green, yellow-green, reddish yellow, or golden brown, in loose mats, often with pendent strands. Primary stems yellow-red, creeping, in cross section with sclerodermis of 4–6 small, thick-walled cells, cortical cells firm-walled, hyaline to yellow, central strand absent; rhizoids sparse, in circular clusters abaxially to the leaf insertions, dark red, smooth to finely roughened, not or sparsely and irregularly branched. Paraphyllia absent. Pseudoparaphyllia absent, scale leaves present over branch buds. Leaves reduced, erect to appressed, broadly ovate-oval, at times panduriform, 1.2–2.0 mm long, apex obtuse-rounded, mucronate to apiculate; leaf cells linear-flexuose, thick-walled, porose, alar cells subquadrate to short rectangular. Secondary stems horizontal, erect or pendent, to 30 cm long, irregularly branched; in cross section with sclerodermis of 4–5 small, thick-walled, reddish orange cells, cortex cells enlarged, firm-walled, pale yellow, central strand absent; axillary hairs 3–5 cells long, reddish throughout, basal cells 1–2, short, quadrate to subquadrate, upper cells 2–3, long-cylindrical; rhizoids not seen. Secondary stem and branch buds short and swollen; leaves broadly oblong-ovate, not ranked, turgid, spreading to erect-spreading from the base, often with one margin broadly twisted inward when dry, erect to erect-spreading when wet, 1.7–3.0 mm long, to 1.6 mm wide, deeply concave, clasping at base, strongly to weakly auriculate; apex acute, generally mucronate, occasionally rounded or shortly apiculate, leaf tips mostly reflexed; margins broadly incurved above, often almost meeting near the apex, entire below, variously serrulate directly below the apex; costa absent; leaf cells linear-flexuose, strongly and consistently porose at base, variously porose to occasionally smooth above, median cells 50–80 x 4–6 μm, basal cells shorter and broader, alar cells bulging in excavate groups, subquadrate to short-rectangular, 10–18 x 8–12 μm, usually dark red or reddish orange. Plants at times with relatively short branches having deciduous leaves. Dioicous. Perigonia gemmate, lateral on secondary stems and branches, 1.0–1.5 mm long, outer perigonial leaves clasping at base, squarrose-recurved above, 0.8–1.0 mm long, inner perigonia leaves broadly ovate, orange-red across the base, cells elongate-flexuose, porose throughout, costa absent; paraphyses and curved-cylindrical antheridia numerous. Perichaetia terminal on short lateral branches, unfertilized perichaetial to 2 mm long; paraphyses and archegonia numerous; leaves clasping below, squarrose above; fertilized perichaetia with densely hairy vaginula; leaves sheathing, outer leaves to 1.5 mm long, inner leaves oblong-lanceolate, long-acuminate, 3.5–4.0 mm long; costa absent, laminal cells long-linear and porose. Setae elongate, 3–15 mm long, smooth below and papillose above or papillose-roughened throughout, red. Capsules exserted, erect, ovoid to short-cylindrical, 1.8–2 mm long; exothecial cells subquadrate to irregularly short-rectangular, firm-walled; stomata superficial in neck; opercula long-rostrate, 1.6–2.0 mm long; annuli rudimentary; peristome diplolepideous, yellowish white, exostome teeth 575 μm long, dorsal (outer) surface lightly horizontally striate at base, finely papillose above, trabeculae weakly developed on both sides, endostome nearly as long as exostome, basal membrane low, segments filamentous, narrowly perforated, papillose, cilia rudimentary or absent. Calyptrae cucullate, 3–6 mm long, densely hairy. Spores oblong, lightly roughened, 36–64 μm long.

Etymology. The specific epithet flexilis is a Latin adjective meaning “pliant or flexible” and refers to its long, flexuose, pendent stems.

Distribution. Mexico; Central America (Belize, Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica, Panama); Caribbean (Cuba, Jamaica, Haiti, Dominican Republic, Puerto Rico, Guadeloupe, Dominica, Martinique); South America (Colombia, Venezuela, Ecuador, Peru, Bolivia, Brazil; Africa (Tanzania, Malagasy Republic).

Illustrations. Bartram (1949, Fig. 118 D–F); Potier de la Varde (1950, Fig. 5); Sharp et al. (1994, Fig. 536); Churchill and Linares (1995, Fig. 126 a–d); Buck (1998, Fig. 90 1–6); Duarte-Bello (1997, Pl. 202); Parra Cuspoca et al. (1999, Fig. 42); Restrepo Restrepo and Para Cuspoca (2000, p. 108–109); Gradstein et al. (2001, Fig. 156 L–O). Figures 3 & 4.

Figure 3. Pilotrichella flexilis. A. Habit. B. Calyptra. C. Spores. D. Capsule and operculum. E. Stem cross section. F. Exostome tooth, dorsal (outer) surface. G. Endostome segment, ventral (inner) surface and part of basal. Scale in mm: bar = 0.08 C & E); bar = 0.09 (F & G); bar = 0.71 (B & D); bar = 5.1 (A). Figures B & D from Britton 100; Figures A, C, E–G from Allen 11549.

Figure 4. Pilotrichella flexilis. A, C, D, G. Leaves. B. Leaf apex and upper margin. E. Median leaf cells. F. Alar cells. Scale in mm: bar = 0.06 (B, E, F); bar = 0.5 (A, C, D, G). Figure A from Pócs & Mwanjabe 6467D (Tanzania); Figures B–F from Allen 11549 (Honduras); Figure G from Pócs 9011/W (Cuba).

Ecology. Often pendent on tree trunks and branches, shrubs, palm fronds, vines, twigs, also on stumps, rotting logs, soil of road banks, boulders, and on ground 600–3200 m (Central America); 550–2600 m (West Indies); 750–3550 m (South America); 1700–2140 m (Africa).

Selected specimens examined. MEXICO. Baja California: Brandegee s.n. (NY); Chiapas: Breedlove 25849 (MO); Guerrero: Croat 45663 (H, MEXU, MO, NY, US); Hidaldo: Pringle, Plantae Mexicanae 10468 (FH, H, JE, L, MO, NY, S); Jalisco: Crum 1061 (NY, US); Oaxaca: Norris 77587 (MO); Puebla: Pringle 10856 (FH); Tamaulipas: Sharp 8713 (FH); Veracruz: Frahm 792298 (B, MO).

CENTRAL AMERICA. BELIZE. Cayo: Allen 15238 (MO); Toledo: Allen 18813 (BRH, MO). GUATEMALA. Alta Verapaz: Standley 92407 (FH, NY); Chimaltenango: Standley 58729 (FH); Chiquimula: Steyermark 30601 (FH); El Progreso: Steyermark 43550 (FH); Guatemala: Standley 80694 (FH, NY); Huehuetenango: Steyermark 48473 (FH, NY, US); Jalapa: Steyermark 32487 (FH); Quezaltenango: Sharp 2207 (FH, MO, US); Sactepéquez: Standley 65103 (FH); San Marcos: Sharp 5472 (NY); Sololá: Steyermark 47236 (FH, MO, NY); Totonicapán: Standley 62651 (FH). EL SALVADOR. Ahuachapán: Monro et al. 2051 (MO); Santa Ana: Davidse et al. 37193 (MO). HONDURAS. Atlántida: Allen 17364 (MO, TEFH); Comayagua: Allen 13999 (MO, TEFH); Cortés: Allen 14221 (MO, TEFH); El Paraíso: Nelson 4799 (MO); Francisco Morazán: Allen 12366 (MO, NY, TEFH); Lempira: Allen 11273 (MO, TEFH); Ocotepeque: Allen 14446 (MO, TEFH); Olancho: Allen 12699 (MO, TEFH). NICARAGUA. Estelí: Stevens 16296 (MO, NIC, NY); Granada: Almedo 1459a (CINN, MO); Jinotega: Henrich & Stevens 421 (MO, NIC, NY); Matagalpa: Davidse et al. 30505 (MO, S); Rivas: Stevens 6543 (MO). COSTA RICA. Alajuela: Croat 43482 (MO); Cartago: King C91-80 (MO); Heredia: Crosby 3879 (MO); Limón: Davidse et al. 25797 (CR, MO); Puntarenas: Lyon 147 (MO); San José: Cryptogamae exsiccatae 3599 (B, BM, H, L, MO, NY, S, US). PANAMA. Bocas Del Toro: Allen 5236 (H, MO); Chiriquí: Allen 5346 (MO); Colón: Croat 33642B (MO); Darién: Allen 8896 (MO).

CARIBBEAN. CUBA. Granma: Pócs & Duany 9083A (MO, NY); Holguín: Acuña & Morton 3916 (NY); Sancti Spíritus: Clément & Léon 6544 (NY); Santiago de Cuba: Buck 7738 (NY); Villa Clara: Pócs & Borhidi 9011/V (MO). JAMAICA. Portland: Crosby 3164 (MO); St. Andrew: Grout, North American Musci Pleurocarpi 389 (H, FH, MO, NY, S, US); St Thomas: Hegewald & Hegewald 8146 (MO). HAITI. Sud: Ekman 606 (NY, S). DOMINICAN REPUBLIC. Peravia: Steere 23177 (NY); Puerto Plata: Reese 15446 (NY); La Vega: Norris 5724 (H, MO, NY). PUERTO RICO. Aguadilla: Steere 5602 (FH, MO, NY); Guayama: Steere 4627 (FH, MO, NY); Humacao: Steere 4018 (MO); Mayagüez: Steere 5514 (FH, MO, NY); Ponce: Steere 6178 (FH, MO). GUADELOUPE. L’Herminier s.n. (FH, NY). DOMINICA. Elliott 669b (FH). MARTINIQUE. Webster 734 (BM).

SOUTH AMERICA. VENEZUELA. Aragua: Pursell et al. 9290 (MO); Barinas: Dorr et al. 4872 (MO, NY); Bolívar: Steyermark & Wurdack 844 (B, FH, MO, NY); Carabobo: Steyermark & Steyermark 95564 (MO); Distrito Federal: Steyermark et al. 127874 (MO); Falcon: Griffin & Wingfield PV-1646 (MO); Lara: Meijer et al. 124 (B, G, H, MO, NY, S, US, VEN); Mérida: Griffin et al. 017476 (H, JE, MO, NY); Monagas: Steyermark 62111b (FH); Portuguesa: Steyermark et al. 126620 (MO); Táchira: Davidse & González 22105 (MO); Trujillo: Liesner et al. 13031 (MO). COLOMBIA. Antioquia: MacDougal et al. 4446 (MO, NY); Boyacá: Churchill et al. 19011 (COL, MO, NY); Cauca: Barclay & Juajibioy 6022-A (MO); Chocó: Churchill et al. 14536 (NY); Magdalena: Mägdefrau 1066 (B); Nariño: Ramírez 10929 (MO); Norte de Santander: Steere 7307 (NY); Putumayo: Ramírez 10286 (MO); Santander: Lewis 88-1307 (B, MO, NY); Valle: Churchill et al. 15342 (CUVC, MO, NY). ECUADOR. Carchi: Steere 9098 (NY); Imbabura: Solís 8264 (NY); Loja: Holm-Nielsen et al. 3679 (MO, S); Morona-Santiago: Steere 27799 (NY); Napo: Steere 9139 (NY); Pastaza: Steere 8425 (NY); Pichincha: Steere & Balslev 25566 (H, NY); Zamora: Steere & Balslev 25826 (NY). PERU. Cajamarca: Campos et al. 5252 (MO); San Martin: Smith C295 (MO). BOLIVIA. Cochabamba: Price et al. 1476 (MO); La Paz: Lewis 89-990 (MO); Santa Cruz: Nee 40677 (MO, NY, S). BRAZIL. Bahia: Harley et al. 26238 (NY); Minas Geraes: Vital & Buck 11535 (NY); Paraná: Bauer, Musci Europ. et Amer. 2248 (BM, FH, H, L, MO, NY, S); Rio de Janeiro: Landrum 2181 (MO, NY); Rio Grande do Sul: Wasum et. al. 4248 (MO); Santa Catarina: Vital & Buck 12382 (NY); São Paulo: Schäfer-Verwimp 6954 (MO).

AFRICA. TANZANIA. Kilosa: Inoue, Bryophyta Selecta Exsiccata 735 (H, JE, MO, NY, S); Morogoro: Pócs 6467/D (MO, NY). MALAGASY REPUBLIC. Antananarivo: Pool s.n. (NY). Antseranana: Crosby & Crosby 7149 (BM, G, FH, H, MO, NY, US).

Pilotrichella flexilis is the most widespread species in the genus, there are thousands of herbarium collections of it. It is frequently encountered in the field growing in dense pendent masses in shaded, very humid places. The species is remarkably stenotypic in most of its features and can often be recognized with a hand-lens by its usually golden-reddish color, turgid appearance, and erect-spreading leaves that are somewhat twisted above when dry and have consistently recurved mucros. Not all leaves in a single collection are liable to have recurved mucros, but the feature can always be found on at least some (usually most) leaves. The leaves near the branch buds are especially likely to have recurved mucros.

The leaves of P. flexilis are absolutely ecostate and consistently have auriculate leaf bases with bulging-excavate, generally dark-red alar cells, linear-flexuose, strongly porose cells, and broadly incurved upper margins. There are some collections of P. flexilis with straight-walled or very weakly porose upper leaf cells. These collections also are consistently green to light-green in color, and this suggests the feature may be associated with even more shaded, humid habitats than is normal for the species. The feature does not appear to be of taxonomic value since there are collections that exhibit all gradations of straight-walled to strongly porose upper leaf cells.

The leaves of P. flexilis are characteristically mucronate, but mucro length varies considerably within the species. Plants at one end of the variation have most leaves with rounded apices; leaves with distinct mucros occur only sporadically. This extreme is geographically centered in African and nomenclaturally centered on P. perrobusta.

Plants from Central and South America, however, occasionally have this type of leaf variation. The opposite extreme occurs in the Caribbean (see i.e., Cuba, Póc & Borhidi 9011/W MO) where some plants with long mucronate leaves closely approach the leaves of P. cuspidans and P. mauiensis. This Caribbean expression of P. flexilis differs from P. cuspidans and P. mauiensis in having distinctly recurved leaf mucros.

Pilotrichella flexilis has exserted, shortly cylindrical capsules on setae that are usually 10 mm long. Its setae, however, vary from 3 mm long to 15 mm long. This variation in seta length does not appear to have taxonomic value since some collections have single stems with setae that range 3 mm to 11 mm long.

The upper leaf margins directly below the apex in P. flexilis are serrulate as the result of projecting cell ends. There seems to be a direct correlation between the degree of upper leaf margin incurving and marginal serrulation. Leaves with the strongest incurved margins have the most distinct marginal serrulations. Some collections of P. flexilis have leaves with entire margins, but even these collections also have some leaves with weakly serrulate upper leaf margins.

Pilotrichella flexilis has been confused with Squamidium nigricans (Hook.) Broth. and Phyllogonium viscosum (P. Beauv.) Mitt. These species are similar to P. flexilis in overall aspect, they grow in pendent masses, and their leaves have recurved mucros. Squamidium nigricans is a smaller plant than P. flexilis, it has spirally ranked leaves, and often the plants have an intense blackish color. It also differs from P. flexilis in having immersed capsules, and leaves with long (but faint) single costae. The alar cells in S. nigricans are more extensively developed than those of P. flexilis, they are often hyaline rather than reddish yellow, and not as strongly bulging as the alar cells of P. flexilis. Phyllogonium viscosum and P. flexilis have auriculate leaves and linear-flexuose, strongly porose leaf cells. The genus Phyllogonium is characterized by its distichous, conduplicate leaves and this feature usually can be relied on to separate it from P. flexilis. Phyllogonium viscosum however has swollen, turgid leaves that tend to obscure the distichous nature of the leaves. The costa in P. viscosum varies from shortly double to absent, and this feature can be used to distinguish it from P. flexilis which is absolutely ecostate.

There is a collection of P. flexilis ( MO) labeled “Bermuda.” The specimen is a duplicate from the “Elizabeth Gertrude Britton Moss Herbarium” at the New York Botanical Garden. There is no duplicate of this specimen at NY. It is very unlikely this specimen came from Bermuda which lacks the habitats and elevation commonly associated with P. flexilis. It seems more plausible that this is a labeling error.

2a. Pilotrichella flexilis form nudiramulosa (C. Müll.) Allen & Magill, forma nova.

Pilotrichella nudiramulosa C. Müll., Hedwigia 40: 85. 1901. Protologue: Brazil. Brasilia, Sa Catharina, Serra Geral, ad truncos Araucariae Brasiliensis: E. Ule, Junio 1890, Coll. No. 867. Lectotype: Brasilia, prov. S. Catharina, Serra Geral, an Stammen von Araucaria, Junii 1890. leg. E. Ule 867 (H).

Etymology. The epithet nudiramulosa combines the Latin adjectives nudus “naked” and ramulosus “bearing branchlets” in reference to its short branches with deciduous leaves.

Distribution. Mexico; Central America (Costa Rica, Panamá); South America (Colombia, Ecuador, Peru, Brazil); Africa (Madagascar).

Illustration. Figure 2 F.

Figure 2F. Pilotrichella flexilis form nudiramulosa. F. Habit. Scale in mm: bar = 5.1 (F). Figure F from the type.

Ecology. On tree trunks and branches; 800–2700 m.

Selected specimens examined. MEXICO. Chiapas: Breedlove 14403 (MO); Hidalago: Vela 598 (US); Veracruz: Arséné 8003 (FH).

COSTA RICA. Alajuela: Brenes 16691 (FH, NY); Cartago: Standley 33582 (FH, US); Heredia: Tonduz s.n. [Pl. Costaricensis N° 5680] (G); Puntarenas: Haber 6211 (CR, MO, NY); San José: Crosby 10882 (CR, MO). PANAMA. Chiriquí: Croat 13746 (MO).

COLOMBIA. Cundinamarca: Apollinaire s.n. (G). ECUADOR. Loja: Loja: André K1801 [8 Nov.] (NY); Pichincha: Spruce 1232 (BM). PERU. Arequipa: André K1801 [17 Nov. 1876] (FH); BRAZIL. Rio Grande do Sul: Lindman 122 (BM, H, S); Santa Catarina: Ule 169 (B, BM, FH, JE, L, NY, S); São Paulo: Wacket 1235 (H).

MALAGASY REPUBLIC. Antseranana: Magill et al. 9948 (MO).

Pilotrichella flexilis form nudiramulosa is generally a smaller plant than most collections of P. flexilis. Typically it has short branches with leaves so deciduous that the branches are often naked. Plants of P. flexilis form nudiramulosa exhibit considerable gametophytic variation throughout their range, especially in the development of deciduous leaves. Gametophytic variation in form nudiramulosa shows more or less discrete geographical patterns, and this may indicate the taxon is not monophyletic. Rather the multiple evolution of this form may have been driven by its deciduous leaves that in a species rarely producing sporophytes would increase the ability of the plant to reproduce asexually.

Pilotrichella mauiensis is similar in size to form nudiramulosa, and sometimes it also has short branches with deciduous leaves. The presence of flagelliform branch tips in P. mauiensis as well as slender branchlets with microphyllous leaves will often distinguish it from P. flexilis form nudiramulosa. Furthermore, the leaves of P. mauiensis are not nearly as auriculate at base as those of P. flexilis, and its usually cuspidate leaf apices are erect rather than recurved.

The ranges of P. flexilis form nudiramulosa and P. mauiensis overlap in Central America and Mexico. Unfortunately, collections of form nudiramulosa in these regions have inconsistently recurved leaf mucros. These collections are exceedingly difficult to distinguish from collections of P. mauiensis that have short cuspidate leaves. When slender branchlets and flagelliform branch tips are also absent from the collections of P. mauiensis with short cuspidate leaves the two taxa are essentially indistinguishable.

3. Pilotrichella mascarenica (C. Müll.) Jaeg., Ber. Thätigk. St. Gallischen Naturwiss. Ges. 1875-76: 259. 1877. Neckera mascarenica C. Müll., Bot. Zeitung (Berlin) 17: 237. 1859. Protologue: Réunion. Insula Borboniae: Bory de St. Vincent. Lectotype: Isle de Bourbon, Bory S^t Vincent (G). Isolectotypes: Isle de Bourbon, Bory S^t Vincent (BM); Bourbon, Bory (L); Mascareignes, Bory de St. Vincent (H).

Pilotrichella isleana Besch., Ann. Soc. Nat., Bot. sér. 6, 10: 267. 1880. Protologue: Réunion. La Réunion: plaine des Cafres, associé au Phyllogonium, G. de L’Isle, 1875. Holotype: La Reunion. Plaine de Cafres, G. de Isle (BM).

Pilotrichella islei Besch. ex Kindb., Enum. Bryin. Exot., Suppl. 2. 102. 1891, orthographical variant of P. isleana Besch..

Pilotrichella hampeana Kiaer in Wright, J. Bot. 26: 266. 1888, invalid name, lacks a description. Based on: Madagascar, Mt. Ankaratra (Borgen 30). Musci Madagascarienses, Herb. Kiaer. In montibus Ankaratra 1877–1879 legit M. Borgen no. 30 (H); Musci Madagascarienses, Herb. Kiaer. In montibus Ankaratra 1875 legit M. Borgen no. 30 (L).

Nomenclatural note. The two specimens on which the name Pilotrichella hampeana is based bear identical printed labels. The label on the specimen from L, however, has the date 1879 inked out and the date 1877 changed to 1875.

Plants small to medium-sized, dull, light green, green, yellow-green, or golden brown, in loose mats often with pendent strands. Primary stems red, creeping, in cross section sclerodermis with 4–5 small thick-walled cells, cortical cells firm-walled, hyaline to yellow, central strand absent; rhizoids sparse, in circular clusters abaxially to the leaf insertions, dark red, smooth, not or sparsely and irregularly branched. Paraphyllia absent. Pseudoparaphyllia absent, scale leaves present over branch buds. Leaves reduced, erect to appressed, broadly ovate-oval, at times panduriform, to 1.4 mm long, apex obtuse-rounded, mucronate to apiculate; leaf cells linear-flexuose, thick-walled, porose, alar cells subquadrate to short-rectangular. Secondary stems arising irregularly from the primary stems, often pendent, to 14 cm, irregularly branched, in cross section sclerodermis with 4–5 small, thick-walled, reddish orange cells, cortex cells enlarged, firm-walled, pale yellow, central strand absent; axillary hairs, 3–4 cells long, basal cells 1–2, short, quadrate to subquadrate, reddish, upper cells 2, long-cylindrical, yellowish; rhizoids rare, at base of branches, dark red, smooth, not or sparsely and irregularly branched. Secondary stem and branch buds short and swollen; leaves oblong-ovate, not ranked, turgid, erect to erect-spreading from the base when dry, erect-spreading when wet, 1.2–1.6 mm long, concave, clasping at base, strongly to weakly auriculate; apices acute, mucronate to shortly apiculate, leaf tips often reflexed; margins broadly incurved above, usually meeting or overlapping near the apex, entire below, variously serrulate below the apex; costa absent; leaf cells linear-flexuose, porose, median cells 30–60 x 3–4 μm; basal cells shorter and broader, alar cells bulging in excavate groups, subquadrate to short-rectangular, 10–28 x 10–20 μm, usually dark red or reddish orange. Dioicous. Perigonia gemmate, lateral on secondary stems and branches, 1.0 mm long, outer perigonial leaves clasping at base, erect to recurved above, 0.8–1.0 mm long, inner perigonia leaves broadly ovate, orange-red across the base, cells elongate-flexuose, porose throughout, costa absent; paraphyses and curved-cylindrical antheridia numerous. Perichaetia terminal on short lateral branches, unfertilized perichaetial to 2 mm long; paraphyses and archegonia numerous; leaves clasping below, squarrose above; fertilized perichaetia with densely hairy vaginula; leaves sheathing, outer leaves to 1.5 mm long, inner leaves oblong-lanceolate, long-acuminate, 3.5–4.0 mm long; costa absent, laminal cells long-linear, porose. Setae elongate, 7–8 mm long, smooth below and papillose above, red or reddish brown. Capsules exserted, erect, ovoid to short cylindrical, 1.5–2 mm long; exothecial cells subquadrate to shortly and irregularly rectangular, firm-walled; stomata superficial in neck; opercula long-rostrate, 1.5 mm long; annuli rudimentary; peristome diplolepideous, yellowish white, exostome teeth 420 μm long, dorsal (outer) surface lightly horizontally striate at base, finely papillose above, trabeculae weakly developed on both sides, endostome 2/3 the exostome length, basal membrane low, segments filamentous, narrowly perforated, papillose, cilia rudimentary or absent. Calyptrae cucullate, 3–4 mm long, densely hairy. Spores oblong, spherical, rounded-triangular, lightly roughened, 34–54 μm long.

Etymology. The specific epithet mascarenica refers to the Mascarene island group (Réunion, Mauritius, Rodrigues).

Distribution. Africa (Malagasy Republic, Réunion).

Illustration. Figure 5.

Figure 5. Pilotrichella mascarenica. A. Habit. B. Leaf apex and upper margin. C. Capsule and operculum. D. Stem leaf. E, F, K. Branch leaves. G. Calyptra. H. Median leaf cells. I. Alar cells and basal leaf margin. J. Stem cross section. Scale in mm: bar = 0.06 (B, H, I); bar = 0.08 (J); bar = 0.51 (C–F, K); bar = 1.3 (G); bar = 2.6 (A). Figures A, D, E, J from Crosby & Crosby 9006; figures B, H, F, I from the type; figures C, G from Crosby & Crosby 5272; Figure K from Borgen 30.

Ecology. On tree bark and twigs, often pendent from trees; 1350–2200 m.

Specimens examined. AFRICA. MALAGASY REPUBLIC. Antananarivo: Crosby & Crosby 5272 (MO), 5383 (MO), Cremers 1763 (MO), Camboué (H, S), Borgen 30 (H, L), Villaume (FH); Antseranana: Dufournet (S); Fianarantsoa: Crosby & Crosby 6830 (MO); Mahajanga: Humbert & Capuron s.n. (S), 29/11 - 1901, indigenous collector (L). REUNION. Arrondissement au Vent: Bory St. Vincent (BM, G, H, L), Een 350 (MO, S), 321 (S); Arrondissement su le Vent: Chauvet, 1894, (FH, S), Crosby & Crosby 9006 (FH, G, H, L, MO, NY, PC, S, US).

Pilotrichella mascarenica is a small to medium sized species with oblong-ovate leaves that have inconsistently recurved apices. It is identical in size to some forms of P. mauiensis, but that species differs from P. mascarenica in having cuspidate leaves with erect apices. Many collections of P. mauiensis also differ from P. mascarenica in having short branches with deciduous leaves, flagelliform branch tips or slender branchlets with microphyllous leaves. Pilotrichella mascarenica is identical to P. flexilis in many features, and both species have enlarged, irregularly shaped spores. The leaves of P. mascarenica, however, have strongly incurved upper leaf margins that commonly overlap just below the apex. It further differs from P. flexilis in having shorter, narrower leaves, and shorter setae.

Pilotrichella mascarenica is the same size as most species of Orthostichella. Typically Orthostichella has spirally arranged (especially branch) leaves, and this feature usually distinguishes it from P. mascarenica. There are some collections of Orthostichella with leaves indistinctly spirally ranked and these can be difficult to distinguish from P. mascarenica. The alar cells in all species of Orthostichella, however, are weakly differentiated and because they are not excavate-bulging the individual cells can be clearly seen.

4. Pilotrichella mauiensis (Sull.) Jaeg., Ber. Thätigk. St. Gallischen Naturwiss. Ges. 1875-76: 255. 1877. Meteorium mauiensis Sull., Proc. Amer. Acad. Arts 3: 182. 1855. Protologue: Hawaii. East Maui, Sandwich Islands; on the north bank of the Crater, at an elevation of 10,200 feet. Holotype: East Maui, Sandwich Islands; on the north bank of the crater Haleakala, U.S.E.E. Wilkes 1838/42 (FH). Isotypes: East Maui - north Bauky [sic] Crater, 10200 ft high! Sandwich Island, Herbarium of the U. S. Exploring Expedition under the Command of Capt. Wilkes (NY); East Maui, Wilkes Expl. Exp. (NY); East Maui - North Bank of Crater - 10200 ft alt. Sandwich Isds. U. S. Ex. Ex. (NY); Hawaii, Wilkes Exped. E. Maui (FH).

Pilotrichella flagellifera Besch., Mexic. Pl. 39. 1872, illegitimate name, protologue includes an earlier name in synonymy. Protologue: Mexico. Mejico (Ehrenberg); Orizaba (Bourgeau). Lectotype. Mexico, Orizaba, 1866: Bourgeau, Herb. Émil Bescherelle: 1900. (BM, designated here). Syntypes. Mexico leg. C. Ehrenberg (BM); Mexico. C. Ehrenberg (BM); Mexico, Orizaba, Herb. Hampe1881 (BM).

Pilotrichella cochlearifolia var. flagellifera Besch., Mém. Soc. Sci. Nat. Cherbourg 16: 223. 1872. Protologue: Mexico. Orizaba (Bourgeau). Lectotype. Mexico, Orizaba, 1866: Bourgeau, Herb. Émil Bescherelle: 1900. (BM, designated here).

Meteorium vulcanicum Mitt. in Seem., Fl. Vit. 395. 1873. Protologue: Hawaii. Hawaii ad montem ignivomen (Macrae! in Herb. Musaei Brit.). Isotype. Owyhee. ad m. ignivomen. Macrae, Jan. 1825, sin. coll. (FH).

Pilotrichella desmoclada C. Müll., Flora 82: 464. 1896. Weymouthia desmoclada (C. Müll.) Broth., Nat. Pflanzenfam. 1(3): 812. 1906. Protologue: Hawaii. Insulae Hawaiicae, sine loco speciali, sed vero-similiter e regionibus altioribus: Dr. Hillebrand. Lectotype: Hawaii: sine loco designato. leg. Dr. Hillebrand (H, designated here). Isotypes: Hawaii: sine loc spec., leg. Dr. W. Hillebrand (FH); Hawaii. leg. Hillebrand (H).

Nomenclatural note.

1. There is some confusion surrounding the types of P. cochlearifolium and P. flagellifera. This is because the type of P. cochlearifolium and one of the syntypes of P. flagellifera have similiar protologues: “Habitat in regno Mexicano, ubi legit Cl. C. Ehrenberg or Mejico (Ehrenberg)”. All available type specimens give only “Mexico leg. C. Ehrenberg” or “Mexico. C. Ehrenberg” on their labels. This group of available type specimens represents two species; the material in BM is P. mauiensis, and the material in H, JE, S is P. flexilis.

Plants medium-sized, dull, light green, yellow-green, or golden brown, in stiff mats, sometimes with pendent strands. Primary stems yellow-red to red, creeping, in cross section sclerodermis with 4–6 thick-walled cells, cortical cells firm-walled, hyaline to yellow, central strand absent; rhizoids in circular clusters abaxially to the leaf insertions, dark-red, smooth to finely roughened, not or sparsely and irregularly branched. Paraphyllia absent. Pseudoparaphyllia absent, scale leaves present over branch buds. Leaves reduced, erect-clasping, broadly ovate, auriculate at base, 0.8–1.0 mm long; apices acuminate, hair-pointed; leaf cells linear-flexuose, thick-walled, strongly porose, alar cells dark red, subquadrate to short rectangular, upper margins serrulate. Secondary stems arising irregularly from the primary stems, creeping or pendent, to 25 cm long, irregularly branched; in cross section sclerodermis with 4–5 small, thick-walled, reddish orange cells, cortex cells enlarged, firm-walled, pale yellow, central strand absent; axillary hairs 4–5 cells long, basal cells 1–2, short, quadrate to subquadrate, reddish, upper cells 2–3, long-cylindrical, reddish; rhizoids present. Secondary stem and branch apices short and swollen; leaves broadly ovate to oblong-ovate, not ranked, wide-spreading to erect-spreading from the base with margins incurved when dry, erect-spreading when wet, 1–2 mm long, concave, clasping at base, rounded to the insertion or weakly auriculate; apex acuminate, long or short cuspidate, leaf tips straight not reflexed; margins broadly incurved above, entire below, serrulate directly below the apex; costa absent; leaf cells linear-flexuose, porose throughout, median cells 16–50 x 3–4 μm; basal cells shorter and broader, alar cells in bulging, excavate groups, subquadrate to short rectangular, 14–20 x 2–12 μm, yellow red, reddish-orange or red. Plants often having slender branches with microphyllous leaves, flagelliform branch tips, or deciduous leaves. Dioicous. Perigonia gemmate, lateral on secondary stems and branches, 1.0–1.3 mm long, outer perigonial leaves clasping at base, squarrose recurved above, 0.8–1.0 mm long, inner perigonia leaves broadly ovate below, long-acuminate above, orange-red across the base, cells elongate-flexuose, porose throughout, costa absent; paraphyses and curved-cylindrical antheridia numerous. Perichaetia terminal on short lateral branches, unfertilized perichaetial to 2.5 mm long; paraphyses and archegonia numerous; leaves clasping below, squarrose above; fertilized perichaetia with hairy vaginula; leaves sheathing, outer leaves to 2.0 mm long, inner leaves oblong-lanceolate, long-acuminate, 3 mm long; costa absent, laminal cells linear and porose. Setae elongate, 5–15 mm long, smooth to lightly roughened below, papillose above, red. Capsules exserted, erect, ovoid to short cylindrical, 1.5–2.0 mm long; exothecial cells subquadrate to short, irregularly rectangular, firm-walled; stomata superficial in neck; opercula long-rostrate, 1.0–1.5 mm long; annuli rudimentary; peristome diplolepideous, yellowish white, exostome to 508 μm long, dorsal (outer) surface lightly horizontally striate at base, finely papillose above, trabeculae weakly developed on both sides, endostome _ the exostome length, basal membrane low, segments filamentous, narrowly perforated, papillose, cilia rudimentary or absent. Calyptrae cucullate, hairy, to 3.5 mm long. Spores round, irregularly rounded to oblong, lightly roughened, 20–28 μm long.

Etymology. The specific epithet mauiensis refers to the Hawaiian island on which the type of the species was collected.

Distribution. Hawaii; Mexico; Caribbean (Cuba); Central America (Belize, Guatemala, Honduras, Nicaragua, Costa Rica, Panamá); South America (Bolivia).

Illustrations. Bartram (1933, Fig. 125). Figures 6 & 7.

Figure 6. Pilotrichella mauiensis. A. Exostome tooth, two endostome segments, and part of basal membrane, ventral (inner) surface. B. Capsule mouth with rudimentary annulus. C. Capsule and operculum. D. Stem cross section. E. Habit. F. Alar cells and basal leaf margin. G. Calyptra. Scale in mm: bar = 0.06 (B, D, F); bar = 0.09 (A); bar = 0.9 C & G); bar = 2.7 (E). Figures A–C, G from Pringle 10417; figure D from the type; figure E from Bryophyta Hawaiica Exsiccata 37; Figure F from Allen 17364.

Figure 7. Pilotrichella mauiensis. A, B, F–H. Leaves. C & D. Leaf apices. E. Primary stem leaf. Scale in mm: bar = 0.06 (C & D); bar = 0.40 (A, B, E–H). Figures A & D from the type (Hawaii); figures B & C from Allen 17364; figures E & G from Bryophyta Hawaiica Exsiccata 37 (Hawaii); figure F from Hermann 28836 (Mexico); figure H from Pringle 10417 (Mexico).

Ecology. On tree trunks, pendent on branches of, shrubs, vines or twigs; 120–3109 m.

Selected specimens examined. HAWAII. Hawaii: Skottsberg 1341 (FH, H, S); Kauai: Small, Mosses of the Hawaiian Islands 10 (F, FH, L, MO, NY, S); Maui: Hoe, Bryophyta Hawaiica Exsiccata 37 (B, FH, H, MO, NY, S); Oahu: Forbes, 2/12–19/09 (FH, L).

MEXICO. Chiapas: Hermann 26405 (H, MO, NY); Guerrero: Croat 45624A (FH, G, H, MO, NY, US); Hidalgo: Pringle, Plantae Mexicanae 10417 (B, BM, FH, G, H, JE, L, MO, NY, S); Jalisco Crum 892 (S); Oaxaca: Maldonado & Martin 237 (MO); Puebla: Cárdenas 89 (H); San Luis Potosi: Ferguson 7 (NY); Tamaulipas: Pursell 5631 (MO); Veracruz: Hermann 28836 (NY).

CUBA. Santiago de Cuba: Clément 309 (NY).

BELIZE. Toledo: Allen 18831 (BRH, MO). GUATEMALA. Alta Verapaz: Standley 90725 (FH); Zacapa: Steyermark 43227 (FH). HONDURAS. Atlántida: Allen 17399A (MO); Lempira: Allen 11596 (MO); Yoro: Allen 13589 (MO). NICARAGUA. Estelí: Stevens & Grijalva 15632 (MO, NIC); Jinotega: Henrich & Stevens 283 (MO); Matagalpa: Granow de la Cerda 2167 (MO, NY). COSTA RICA. Alajuela: Brenes 16985 (NY); Cartago: Standley 41487 (FH, JE, S, US); Guanacaste: Dodge et al. 7915 (FH); Heredia: Crosby 10870 (H, NY); Puntarenas: Croat 47131 (MO); San José: Stevens 13704 (MO). PANAMA. Chiriquí: Croat 16057 (MO, S).

BOLIVIA. Santa Cruz: Herzog 3991 (JE).

Pilotrichella mauiensis was described from the Hawaiian islands and the species exhibits considerable variation there in plant size and overall aspect. Bartram (1933), however, considered the leaf characters of the species so consistent that he included all of its forms in a single species. The Hawaiian collections of P. mauiensis are instructive in showing important variations not only in plant size and aspect, but in leaf cuspid length, as well as the presence/absence of both flagelliform branch/stem apices and slender branchlets with microphyllous leaves. The plant variations exhibited by the Hawaiian plants, however, do not demonstrate the full range of variation found in the species. For example, plants of P. mauiensis from southern Mexico, Guatemala, Belize, and northern Honduras can be especially robust and have long-cuspidate leaves (see e.g., Hermann 28836 NY or Allen 17364 MO). When first encountered this extreme Neotropical expression seems to be distinct from the Hawaiian P. mauiensis. The species, however, when taken as a whole shows complete intergradation in size and leaf cuspid length. Furthermore, leaf cuspid length is remarkably variable within single collections. Critical features that separate P. mauiensis from other members of Pilotrichella include its erect, usually cuspidate leaf apices, weakly auriculate leaf bases, alar cells differentiated in a relatively small, discrete area, the occurrence of flagelliform branch apices, and the presence of slender branchlets with microphyllous leaves.

Although the slender branchlets in this species appear to be axillary, they in fact arise on the dorsal side of the leaf from the line of alar cells that marks the transition from the alar region to the laminal cells. Since they originate from a single cell they are extremely deciduous. When young the branchlets have the same appearance as the axillary propagula found in Pohlia Hedw., and as they begin to elongate they look similar to the axillary brood branches of Pseudotaxiphyllum elegans (Brid.) Iwats. When fully formed they can be 15 mm long and have microphyllous leaves with axillary brood bodies. These branchlets also occur around branch primordia. Newton (2002) gives an excellent, detailed account of these branchlets. Newton (2002) attributes these structure to P. flexilis, but flagelliform branchlets are unknown in that species and her plants almost certainly are P. mauiensis.

The leaf apices of P. reesei and P. mauiensis are similar, and both species have short, swollen apical buds as well as slender branchlets. Pilotrichella reesei, however, never has flagelliform branch apices, and its leaves are distinctly auriculate with extensively developed alar cells. Furthermore, the leaves of P. reesei differ from those of P. mauiensis in occasionally having shortly mucronate, recurved apices.

The leaves of P. flexilis and P. mauiensis are similar in the form and distribution of their alar cells, and both species can have deciduous leaves. Plants of P. flexilis are generally larger than those of P. mauiensis, and their leaf apices are more consistently mucronate with most of the apices distinctly recurved. Pilotrichella flexilis also never has flagelliform branch apices or slender branchlets.

5. Pilotrichella reesei Allen & Magill, sp. nov.

TYPE: Dominican Republic. Prov. La Vega: 12 km S of Constanza on road to Valle Nuevo, 6000 feet, 18°52'N, 70°42'W, 9 January 1987, William R. Buck 14015 (holotype NY).

Species haec a P. cuspidanti foliis breviter cuspidatis vel mucronatis differt.

Plants slender to medium-sized, dull, light green, yellow-green, reddish yellow, or golden brown, in loose or stiff mats, at times with pendent strands. Primary stems yellow-red, creeping, in cross section sclerodermis with 4–6 cells thick-walled cells, cortex cells enlarged, thick-walled, hyaline to yellow, central strand absent; rhizoids sparse, in circular clusters abaxially to the leaf insertions, dark-red, smooth to finely roughened, not or sparsely and irregularly branched. Paraphyllia absent. Pseudoparaphyllia absent, scale leaves present over branch buds. Leaves reduced, erect to appressed, broadly ovate, auriculate at base, 0.9–1.5 mm long, acuminate, hair-pointed; cells linear-flexuose, thick-walled, porose, alar cells dark red, subquadrate to short rectangular, upper margins serrulate. Secondary stems arising irregularly from the primary stems, often pendent, to 10 cm long, irregularly branched; in cross section sclerodermis with 4–5 small, thick-walled reddish orange cells, cortex cells enlarged, firm-walled, pale yellow, central strand absent; axillary hairs reddish throughout, 3–5 cells long, basal cells 1–2, short, quadrate to subquadrate, upper cells 2–3, long-cylin