21. FISSIDENTACEAE Schimper

Ronald A. Pursell

Plants tiny to robust. Stem, except for initial stages, growing from a 2-sided apical cell. Leaves distichous, equitant, complex in form, consisting of two vaginant laminae that clasp the stem, a ventral lamina located above the vaginant laminae, and a dorsal lamina that occupies the length of the leaf opposite the vaginant and ventral laminae; costa single, usually well developed, near center of leaf, sometimes reduced, absent or nearly so. Seta elongate. Capsule cylindric, 1 2 peristome single, teeth 16, haplolepidous, endostomate, usually divided /2– /3 their length, sometimes irregularly divided or undivided, sometimes reduced, (rarely absent). Calyptra cucullate. Genus 1, species 450 (37 in the flora): worldwide, mostly tropics. Fissidentaceae is recognized easily by its distichous and equitant leaves. This leaf form is closest to that of Bryoxiphium. The hepatic Diplophyllum is often confused with Fissidens. Relationship of the Fissidentaceae is with the Dicranaceae; both families have similar peristomes but differ principally in leaf structure.

1. FISSIDENS Hedwig, Sp. Musc. Frond., 152. 1801 · [Latin fissus, cleft, and dens, tooth, alluding to split peristome teeth]

Moenkemeyera Müller Hal.; Octodiceras Bridel

Plants pale to dark green, sometimes becoming brownish to blackish, particularly in older parts, scattered to forming dense mats. Stems monomorphic or dimorphic, erect, usually becoming decumbent, unbranched and branched; axillary hyaline nodules present or absent, when present composed of 1–3 enlarged, bulging, hyaline cells arranged linearly (larger, multicellular, protruding); epidermal and subepidermal cells small, incrassate, pigmented or not, or enlarged, thin-walled, hyaline; cortical cells larger, thin-walled, hyaline; central strand present or absent; rhizoids tan to reddish, basal and axillary, usually smooth, infrequently papillose; axillary hairs 1-seriate, filiform. Leaves in few to numerous pairs, pinnately or palmately arranged, changing little to strongly crispate when dry, ovate to linear-lanceolate; vaginant laminae mostly acute,

331 332 FISSIDENTACEAE · Fissidens equal, ending on or near margin, or unequal, minor lamina ending between costa and margin, or, particularly in perichaetial leaves, rounded and free distally or narrowed and ending on or near costa; margin entire to serrate, marginal cells often differentiated into a limbidium; costa usually distinct, infrequently obscured, variable in length, absent or nearly so to short-excurrent, variable in structure (bryoides-type, oblongifolius-type, taxifolius-type; laminal cells usually eguttulate, rarely guttulate, 1-stratose, or 2-stratose in patches, rarely 3- or more stratose, smooth, plane, bulging, mammillose, 1-papillose, or pluripapillose, small, firm-walled, rounded to irregularly hexagonal, changing little when dry, to large, thin-walled, hexagonal to oblong cells, usually shrunken when dry [rarely prosenchymatous]. Specialized asexual reproduction uncommon [by globose, multicellular, subterranean gemmae (tubers) or axillary, stalked, multicellular, clavate or filiform gemmae], rarely by chlorophyllose, branched filaments at bases of leaves. Sexual condition dioicous, autoicous, or rarely synoicous. Perigonia gemmiform, axillary, or at bases of stems, or sometimes scattered among persistent protonemata on substratum, or terminal on longer stems. Perichaetia terminal on main stems and long branches, or terminal on short axillary branches. Seta 1–2 [rarely more], smooth [papillose], straight or flexuous, yellow when young, darkening with age, or reddish. Capsule usually exserted, theca erect or infrequently ± inclined, infrequently arcuate, radially or bilaterally symmetric, ovoid to cylindric, smooth, usually stomatose, rarely estomatose, stomata few, in proximal part of theca, phaneroporous; exothecial cells quadrate to oblong, longitudinal walls often thicker than cross walls, frequently collenchymatous; annulus none, abscission zone present; peristome variable; operculum conic, short- to long-rostrate. Calyptra mostly cucullate, infrequently mitrate, smooth or prorate. Spores smooth to finely papillose. Species ca. 450 (37 in the flora): worldwide, mainly tropical areas. Stems of a few species of Fissidens (F. arcticus, F. curvatus, F. scalaris, F. sublimbatus, F. taylorii) are here described as dimorphic: the fertile (perichaetial) stems are conspicuously shorter with fewer pairs of leaves than the infertile stems. Axillary hyaline nodules are arrested branch primordia, discussed in detail by Z. Iwatsuki and R. A. Pursell (1980). These structures are weakly developed in species found in the Western Hemisphere, but are well developed in some African and Asian species. Most species in the flora area have small, incrassate epidermal and subepidermal cells that are usually pigmented. One species, F. hyalinus, however, has large, thin-walled, hyaline epidermal and subepidermal cells that collapse when dry. Most species in the flora area have pinnately arranged leaves on elongate stems. Short-stemmed expressions of F. amoenus, F. closteri, F. exilis, F. hyalinus, F. serratus, and F. zollingeri have leaves palmately arranged. In the majority of species in the flora area the vaginant laminae where joined at their distal ends form an angle of less than 90°, a condition referred to as acute. In most species the vaginant laminae are unequal in size, the smaller of the two is the minor lamina, while the larger is the major lamina, which appears to be a continuation of the ventral lamina. Vaginant laminae are equal in size when their juncture ends on the leaf margin. The vaginant laminae can be fused along the entire length of their distal ends, or the distal end of the minor lamina can be rounded and free (as in Fissidens asplenioides) or narrowed toward the costa, ending on or near the costa (as in F. exilis). These last two conditions are particularly common in perichaetial leaves. Marginal leaf cells in some species in the flora area are differentiated into a limbidium, a band of 1-stratose to multistratose, hyaline to yellowish, prosenchymatous stereid cells. A stereid cell is elongate, typically has sharply pointed ends, and has a wall thicker than the diameter of the lumen. The limbidium is expressed on all laminae in Fissidens appalachensis, F. bryoides, F. crispus, F. curvatus, F. hyalinus, F. minutulus, F. ventricosus, and F. zollingeri. In F. arcticus, F. obtusifolius, F. scalaris, F. sublimbatus, and F. taylorii the limbidium is developed best on the Fissidens · FISSIDENTACEAE 333 vaginant laminae but can be found on the other laminae, particularly in the more robust leaves. In F. amoenus, F. elegans, F. hallianus, F. leptophyllus, F. pallidinervis, and F. submarginatus the limbidium is essentially restricted to the vaginant laminae, sometimes only of perichaetial leaves. Fissidens asplenioides is typically elimbate, but a short limbidium occurs on the vaginant laminae at times. Fissidens pellucidus and F. serratus, although generally elimbate, infrequently have a limbidium on the vaginant laminae of perichaetial leaves. Leaves of F. adianthoides and F. dubius generally show a marginal band of lighter cells that differ from other laminal cells only in depth and slightly thicker walls. This band of lighter cells should not be interpreted as a limbidium. Studies of transverse sections of costa (M. A. Bruggeman-Nannenga 1990) have resulted in the recognition of three basic costal types: bryoides-, oblongifolius-, and taxifolius-types. All are represented in the flora. The oblongifolius-type (see illustration of Fissidens asplenioides) is characterized by three stereid bands (two lateral and one adaxial) in the proximal part of leaf. There are as many as 16 peripheral guide cells and as many as five large central cells separating these stereid bands. In the bryoides- and taxifolius-types (see illustrations of F. pallidinervis and F. taxifolius, respectively) there are two stereid bands (both lateral) in the proximal part of leaf. However, in the taxifolius-type there are four or more peripheral guide cells and as many as five large central cells separating the stereid bands, while in the bryoides- type there are two peripheral guide cells and usually just a single large central cell. One species in the flora, F. exilis, has costa reduced in structure and another species, F. hyalinus, is essentially ecostate, the costa represented by a proximal vestige. Fissidens pellucidus is the only species in the flora area in which small, clear, dotlike structures called guttulae (E. S. Salmon 1899) are present in the laminal cells. The nature of guttulae is not known. These guttulae can easily be mistaken for papillae. The surface of laminal cells in Fissidens is variable: smooth and either plane or bulging, mammillose, 1-papillose, and pluripapillose. A smooth, plane surface is flat while a smooth, bulging surface protrudes slightly outward. A mammillose cell can be difficult to distinguish from a 1-papillose cell; both have a single hollow protuberance, but the former is more or less rounded while the latter is sharp- pointed. The presence of a few small, localized thickenings characterize a pluripapillose cell wall. The seminal study by B. H. Allen (1980), followed by the study by M. A. Bruggeman- Nannenga and W. Berendsen (1990), established that variations in peristome teeth are useful in determining natural relationships in Fissidens. Of the different peristome types recognized, the bryoides-, scariosus-, taxifolius- and similiretis-types are represented in the flora. In the bryoides- and taxifolius-types the trabeculae on the exterior surface of the undivided parts are higher and distinct from the lamellae. On the other hand, the trabeculae on the exterior surface of the undivided parts in the scariosus- and similiretis-types are indistinct from the equally high or higher lamellae. Variations also occur in the ornamentation in the area of bifurcation. In the taxifolius-type this ornamentation on the exterior surfaces of the undivided parts changes gradually, while in the other types there is a sudden change. The distal ends of the filaments in the bryoides- and scariosus-types are spirally thickened while in the similiretis-type they are squamose. The distal ends of the filaments in the taxifolius-type have protruding (nodose) trabeculae with spiral or vertical lamellar thickenings. In addition to these types there are anomalous peristomes that do not fit into any of the types described. Capsule in the majority of species in the flora are exserted on elongate setae. However, in F. fontanus, F. hallianus, and F. ventricosus the setae are short so that the capsules are emergent, not extending beyond the perichaetial leaves. 334 FISSIDENTACEAE · Fissidens Fissidens is divided into four subgenera (R. A. Pursell and M. A. Bruggeman-Nannenga 2004): Aloma (Müller Hal.) Kindberg, Fissidens, Octodiceras (Bridel) Brotherus, and Pachyfissidens (Müller Hal.) Kindberg. Aloma is not further divided. Fissidens is divided into sections Fissidens and Sarawakia (Müller Hal.) Pursell & Bruggeman-Nannenga, the latter not represented in the flora area. Octodiceras is not subdivided. Pachyfissidens is divided into sections Amblyothallia Müller Hal., Crispidium Müller Hal., and Pachyfissidens. Crispidium is not represented in the flora area. Hedwig, obviously impressed with the similarity of the leafy stems of Fissidens with the fronds of ferns, coined several specific epithets reflecting this likeness. Thus, adianthoides, asplenioides, osmundioides, and polypodioides allude to the fern genera Adiantum, Asplenium, Osmunda, and Polypodium, respectively. The specific epithet taxifolius alludes to similarity with the leaves of Taxus (yew).

1. Leaves ecostate or essentially so...... 37. Fissidens hyalinus 1. Leaves costate. 2. Leaves elimbate ...... Key A 2. Leaves limbate. 3. Limbidium on all laminae ...... Key B 3. Limbidium confined to vaginant laminae. 4. Laminal cells smooth, plane, sometimes bulging ...... Key C 4. Laminal cells mammillose or pluripapillose ...... Key D

Key A. Leaves costate, elimbate

1. Laminal cells mammillose or papillose. 2. Laminal cells mammillose or 1-papillose. 3. Mammillae present, ± restricted to vaginant laminae ...... 7. Fissidens taxifolius 3. Mammillae or papillae on all laminae. 4. Marginal cells of dorsal and ventral laminae not differing greatly in shape from inner cells; marginal cells of vaginant laminae coarsely and irregularly serrate ...... 28. Fissidens serratus (in part) 4. Marginal cells on dorsal and ventral laminae mostly oblate, differing in shape from inner cells; marginal cells of vaginant laminae regularly to irregularly crenulate ...... 32. Fissidens littlei 2. Laminal cells pluripapillose (best seen on vaginant laminae). 5. Papillae restricted to corners of vaginant laminal cells, inconspicuous (best seen in transverse section of leaf) ...... 9. Fissidens bushii 5. Papillae over lumina of cells, not restricted to vaginant laminae, conspicuous. 6. Leaf apex absent a clear, sharp cell ...... 26. Fissidens pallidinervis (in part) 6. Leaf apex ending in a clear, sharp cell...... 27. Fissidens elegans (in part) 1. Laminal cells smooth, often bulging but not mammillose. 7. Laminal cells regularly pluristratose; plants usually coarse to the touch, usually found in rapidly running water ...... 11. Fissidens grandifrons 7. Laminal cells 1- or 2-stratose in patches, never regularly pluristratose; plants not coarse to the touch; found on various terrestrial substrates or aquatic. 8. Leaves often 10 or more times as long as wide, fragile when dry; plants feathery in appearance, most often profusely branched; plants usually in quiet waters. 9. Costa ending 15–35 cells before leaf apex; sporophytes 1–5, axillary; capsules emergent; peristome teeth reduced, usually truncate ...... 12. Fissidens fontanus 9. Costa ending 5–15 cells before leaf apex; sporophytes 1–2, terminal; capsules exserted; peristome teeth complete, undivided or divided ...... 13. Fissidens hallianus (in part) Fissidens · FISSIDENTACEAE 335

[8. Shifted to left margin.—Ed.] 8. Leaves usually less than 10 times as long as wide, not fragile when dry; plants not feathery in appearance, unbranched to moderately branched; plants on various terrestrial substrates. 10. Distal part of costae obscured by overlying chlorophyllose cells ...... 8. Fissidens subbasilaris 10. Costae conspicuous throughout length, not covered by overlying chlorophyllose cells. 11. Leaves in transverse section showing an oblongifolius-type of costa in proximal half of leaf. 12. Plants usually robust; leaf apex rounded to broadly acute; minor laminae of many leaves rounded distally and free; medial marginal cells of vaginant laminae elongate, oriented obliquely; costa in distal part of leaf in transverse section showing a single row of enlarged cells ...... 1. Fissidens asplenioides (in part) 12. Plants small; leaf apex abruptly narrowed, rounded-obtuse; minor lamina ending near leaf margin; medial marginal cells of vaginant lamina not differing from inner cells; costa in distal part of leaf in transverse section showing 4 enlarged cells arranged in 2 rows ...... 2. Fissidens santa-clarensis 11. Leaves in transverse section showing either a taxifolius-, bryoides-type or reduced costa in proximal half of leaf. 13. Plants 10–50 mm; costa taxifolius-type. 14. Laminal cells commonly 2-stratose in patches; leaf apex unevenly serrate ...... 5. Fissidens dubius 14. Laminal cells 1-stratose, rarely 2-stratose in patches; leaf apex regularly crenulate to serrulate to ± denticulate. 15. Perichaetia and sporophytes terminal; rhizoids papillose . . . . 6. Fissidens osmundioides 15. Perichaetia and sporophytes on short axillary branches, usually near distal end of stem; rhizoids smooth. 16. Leaf margin entire but denticulate at leaf apex; leaf apex obtuse to broadly acute, usually bluntly mucronate ...... 3. Fissidens polypodioides 16. Leaf margin crenulate to regularly serrulate; leaf apex mostly acute. 17. Plants to 85 mm; costa ending 2–3 cells before apex to percurrent; laminal cells 10–20 µm ...... 4. Fissidens adianthoides 17. Plants to 17 mm; costa ending several cells before leaf apex to excurrent, even in same plant; laminal cells 6–15 µm ...... 10. Fissidens aphelotaxifolius 13. Plants smaller, 0.6–4.5 mm.; costa bryoides-type or reduced. 18. Leaf apex rounded to obtuse ...... 21. Fissidens obtusifolius (in part) 18. Leaf apex acute, obtuse-apiculate or obtuse-mucronate. 19. Juxtacostal cells in proximal parts of vaginant laminae enlarged, oblong, pellucid ...... 22. Fissidens amoenus (in part) 19. Juxtacostal cells in proximal parts of vaginant laminae not greatly enlarged, oblong, nor pellucid. 20. Vaginant laminae with 2–3 rows of irregularly elongate intralaminal cells; protonemata persistent ...... 34. Fissidens exilis 20. Vaginant laminae absent rows of irregularly elongate intralaminal cells; protonemata not persistent. 21. Costa percurrent; minor lamina of all leaves narrowed distally, ending on costa ...... 36. Fissidens closteri 21. Costa ending before apex; minor lamina usually ending ± the distance between costa and margin or nearly so. 22. Costa ending 3–7 cells before leaf apex; medial laminal cells 14–18 µm, laminal cells guttulate ...... 31. Fissidens pellucidus 22. Costa ending 6–15 cells before leaf apex; medial laminal cells 10–54 µm; laminal cells eguttulate ...... 33. Fissidens pauperculus 336 FISSIDENTACEAE · Fissidens

Key B. Leaves costate, limbate on all laminae, laminal cells smooth, plane to bulging

1. Stems dimorphic. 2. Limbidium confluent at leaf apex with costa, well developed on most leaves; limbidial cells 2- to 3-stratose; peristome typical bryoides-type ...... 18. Fissidens curvatus 2. Limbidium ending before leaf apex, best developed on perichaetial and subtending leaves, often confined to vaginant laminae; limbidial cells 1-stratose; peristome bryoides-type or anomalous. 3. Peristome anomalous, teeth papillose distally, undivided, imperfectly divided or divided 4/5 their length, even in same capsule ...... 20. Fissidens scalaris (in part) 3. Peristome bryoides-type. 4. Laminal cells small, 6–11 µm, bulging, obscure, ± arranged in discernable rows distally ...... 24. Fissidens sublimbatus (in part) 4. Laminal cells larger, 6–18 µm, ± plane, distinct, not arranged in discernable rows distally. 5. Dorsal lamina typically ending well above insertion; limbidium often confined to vaginant laminae of leaves other than perichaetial leaves; the Arctic ...... 17. Fissidens arcticus (in part) 5. Dorsal lamina typically ending at or very near insertion; limbidium variable, absent at times on some leaves; Arkansas, California ...... 19. Fissidens taylorii 1. Stems monomorphic. 6. Limbidial cells 2- to pluristratose; plants in running water. 7. Limbidium confluent with costae in leaf apex; capsules exserted; eastern North America ...... 14. Fissidens appalachensis 7. Limbidium ending a few cells before leaf apex; capsules emergent; Pacific Coast, Idaho ...... 15. Fissidens ventricosus 6. Limbidial cells 1-stratose, sometimes 2- to 3-stratose; plants not commonly found in running water. 8. Leaf apex obtuse to rounded, not apiculate ...... 21. Fissidens obtusifolius (in part) 8. Leaf apex neither rounded nor obtuse, if obtuse then apiculate, leaves mostly lanceolate to oblong. 9. Laminal cells 6–18 µm, ± plane, distinct. 10. All cells in vaginant laminae ± similar, neither greatly enlarged, nor ± oblong, nor pellucid ...... 16. Fissidens bryoides (in part) 10. Groups of juxtacostal cells in proximal parts of vaginant laminae greatly enlarged, oblong, pellucid ...... 35. Fissidens zollingeri 9. Laminal cells small, 6–11 µm, bulging, ± obscure. 11. Distal laminal cells not arranged in discernable rows; plants unbranched ...... 25. Fissidens minutulus 11. Distal laminal cells arranged in discernable rows; plants usually branched. 12. Dorsal lamina ending near insertion to ± decurrent; limbidium on most leaves ...... 23. Fissidens crispus 12. Dorsal lamina ending well above insertion; limbidium best developed on perichaetial and distal leaves, usually confined to vaginant laminae on infertile stems ...... 24. Fissidens sublimbatus (in part)

Key C. Leaves costate, limbate; limbidium confined to vaginant laminae; laminal cells smooth, plane, sometimes bulging

1. Stems dimorphic. 2. Peristome anomalous, teeth papillose distally, smooth proximally, undivided, imperfectly divided, or divided 4/5 their length, even in same capsule ...... 20. Fissidens scalaris (in part) 2. Peristome bryoides-type. Fissidens · FISSIDENTACEAE 337

3. Laminal cells 6–18 µm, ± plane, distinct, not arranged in discernable rows distally ...... 17. Fissidens arcticus (in part) 3. Laminal cells 6–11µm, bulging, ± obscure, ± arranged in discernable rows distally ...... 24. Fissidens sublimbatus (in part) 1. Stems monomorphic. 4. Limbidium restricted to perichaetial leaves. 5. Juxtacostal cells in proximal part of vaginant laminae not conspicuously enlarged nor pellucid ...... 16. Fissidens bryoides (in part) 5. Juxtacostal cells in proximal part of vaginant laminae conspicuously enlarged, ± oblong, pellucid ...... 22. Fissidens amoenus (in part) 4. Limbidium present on perichaetial and cauline leaves. 6. Plants usually floating in quiet waters; leaves sometimes 10:1...... 13. Fissidens hallianus (in part) 6. Plants usually not aquatic, but sometimes inunduated by fluctuating water levels; leaves less than 10:1. 7. Proximal half of leaf in transverse section showing oblongifolius-type costa; minor lamina usually rounded and free distally in most leaves ...... 1. Fissidens asplenioides (in part) 7. Proximal half of leaf in transverse section showing bryoides-type costa; minor lamina acute, attached along entire distal end. 8. Leaf apex neither rounded nor obtuse, if obtuse then apiculate; leaves mostly oblong to lanceolate...... 16. Fissidens bryoides (in part) 8. Leaf apex obtuse to rounded; leaves ovate to oblong . . . . 21. Fissidens obtusifolius (in part)

Key D. Leaves costate, limbate; limbidium confined to vaginant laminae; laminal cells mammillose, 1-papillose, or pluripapillose

1. Laminal cells pluripapillose. 2. Leaf apex not ending in a clear sharp cell ...... 26. Fissidens pallidinervis (in part) 2. Leaf apex ending in a clear sharp cell ...... 27. Fissidens elegans (in part) 1. Laminal cells mammillose or 1-papillose. 3. Limbidium confined to perichaetial leaves; leaf margin, other than limbate parts, serrate, often coarsely so on vaginant laminae ...... 28. Fissidens serratus (in part) 3. Limbidium on most leaves; leaf margin, other than limbate parts, crenulate-serrulate to serrulate. 4. Limbidium along entire length of vaginant laminae, sometimes extending a short distance onto proximal part of adjoining ventral lamina ...... 29. Fissidens submarginatus 4. Limbidium confined to proximal 1/3–1/2 of the vaginant laminae ...... 30. Fissidens leptophyllus

1. Fissidens asplenioides Hedwig, Sp. Musc. Frond., distally, elimbate except for a weak limbidium in the 156. 1801 proximal parts of vaginant laminae, limbidial cells 1- Plants to 250 × 4 mm. Stem stratose; costa ending several cells before apex, unbranched and sparingly oblongifolius-type, distal part of leaf in transverse section branched; axillary hyaline nodules showing enlarged cells arranged in a single row; laminal weak; central strand present. cells of dorsal and ventral laminae 1-stratose, distinct, Leaves in as many as 25 pairs, smooth, lenticularly thickened but appearing bulging, often undulate, mostly lingulate, firm-walled, irregularly hexagonal, 7–12 µm long;

5 5 juxtacostal and interior proximal cells of vaginant 5 rounded to obtuse to broadly 5 5 5 5 acute, sometimes apiculate, to 4 × laminae 1-stratose, smooth, plane, quadrate to ± oblong, 0.5 mm; dorsal lamina narrowed larger; medial marginal cells of vaginant laminae proximally, ending before or at insertion, not decurrent; ± elongate, oriented obliquely. Sexual condition dioicous; perigonia and perichaetia on elongate stems; naked vaginant laminae 1/2–3/4 the leaf length, unequal, minor lamina of most leaves rounded and free distally, or archegonia at times in axils of distal leaves. Sporophytes narrowed distally and ending on or near costa; margin 1–2 per perichaetium, orange-red. Seta to 6 mm. Capsule ± entire to crenulate-serrulate, sometimes unevenly so theca ± erect, radially symmetric to slightly arcuate, 338 FISSIDENTACEAE · Fissidens

FISSIDENS

bilaterally symmetric, to 1.5 mm; peristome taxifolius- 2. Fissidens santa-clarensis Thériot, Mem. Soc. Cub. type; operculum ± as long as theca. Calyptra cucullate, Hist. Nat. “Felipe Poey” 13: 209, plate 32, fig. 1. 1939 smooth, 1–1.7 µm. Spores 7.5–12 µm. Sandstone ledges and crevices in moist ravines and Fissidens allenianus Bruggemann- grottoes, usually along streams and waterfalls; Ala., Ga., Nannega & Pursell Ky., La., Miss., N.C., S.C.; Mexico; West Indies; Central America; South America; Asia; Africa; Atlantic Islands Plants to 7.5 × 1.5–2.5 mm. (Macaronesia); Pacific Islands (New Zealand); Australia. Stem unbranched and branched; Fissidens asplenioides, usually a robust species, is axillary hyaline nodules absent; recognized by leaves typically curled tightly inward from central strand present or absent. Leaves as many as 25 pairs, the tips when dry, a minor lamina that in most leaves is 5 rounded distally and attached more or less only along often undulate, oblong-lingulate, costa, lenticularly thickened dorsal and ventral laminal abruptly narrowed to rounded- cells, elongate medial marginal cells of the vaginant obtuse apex, 1.2–2 × 0.3–0.4 mm; dorsal lamina laminae oriented obliquely, and oblongifolius-type costa narrowed proximally, rounded, ending a short distance 1 2 which in the distal part of the leaf in transverse section before insertion; vaginant laminae /2– /3 the leaf length, shows a single row of enlarged cells. The oblongifolius- acute, ± unequal, minor lamina ending near margin; type costa, found in F. asplenioides and F. santa-clarensis, margin crenulate, elimbate; costa ending 4–10 cells before is unique to sect. Amblyothallia of subg. Pachyfissidens apex, oblongifolius-type, distal part of leaf in transverse (R. A. Pursell and M. A. Bruggeman-Nannenga 2004). section showing 4 enlarged cells arranged in 2 rows; Subterranean, multicellular, irregularly globose, rhizoidal laminal cells in dorsal and ventral laminae 1-stratose, gemmae have been reported in Macaronesian specimens distinct, lenticularly thickened but appearing mammillose, of F. asplenioides. firm-walled, irregularly hexagonal, 6–9 µm, juxtacostal and interior cells of vaginant laminae 1-stratose, smooth, plane, larger; medial marginal cells of vaginant laminae not differing perceptively from interior cells. Sexual Fissidens · FISSIDENTACEAE 339 condition cladautoicous; perigonia and perichaetia on Fissidens polypodioides is a robust species and has its main stems and branches. Sporophytes 1 per greatest distribution in the neotropics and Asia. It is perichaetium. Seta to 4.5 mm. Capsule theca erect, perhaps the handsomest species of the genus in the flora radially symmetric, 0.3–1 mm; peristome similiretis-type; area. However, it might be confused with F. asplenioides, operculum 0.5–0.6 mm. Calyptra 0.7–0.8 mm. Spores from which it is distinguished by taxifolius-type costa, 11–15 µm. leaves crisped but not curled tightly inward when dry, Rotten wood, bark of living trees, particularly around entire leaf margin, acute and more or less equal vaginant the base, moist soil, and limestone; Fla.; Mexico; West laminae, larger laminal cells that are not lenticularly Indies; Central America. thickened, and absent differentiated medial marginal cells Fissidens santa-clarensis, named for a province in in the vaginant laminae. The central strand is especially Cuba, is restricted in the United States to peninsular well developed. H. A. Crum and L. E. Anderson (1965, Florida (Citrus, Collier, Dade, Levy, Manatee, Marion, 1981) published illustrations of F. polypodioides and F. Monroe, Polk, and Sumter counties). The species can be asplenioides that aid greatly in distinguishing the two. recognized by its abruptly narrowed, rounded-obtuse leaf apex, lenticularly-thickened dorsal and ventral laminal 4. Fissidens adianthoides Hedwig, Sp. Musc. Frond., cells, short oblongifolius-type costa that in transverse 157. 1801 section of the distal part shows four enlarged cells Fissidens adianthoides var. arranged in two rows, and similiretis-type of peristome. 5 immarginatus Lesquereux & James

Collections of F. santa-clarensis were long assigned by 5

5 5 Plants to 85 × 5 mm. Stem mostly American authors to F. radicans Montagne, a closely 5 branched; axillary hyaline nodules 5 related species with caducous leaves, a broadly acute to 5 5 5 5 5 5 5 5 absent; central strand present. 5 5 rounded leaf apex, and an anomalous peristome with 5 5 5 5 5 5 5 5 5 55 5 5 5 5 5 5 5 5 5 Leaves as many as 60 pairs, 5 5 5 5 5 teeth undivided or irregularly divided. 5 5 5 5 5 5 5 5 5 somewhat undulate, oblong to 5 3. Fissidens polypodioides Hedwig, Sp. Musc. Frond., lanceolate, acute, occasionally 154. 1801 obtuse, to 3.5 × 1.2 mm; dorsal lamina rounded or narrowed proximally, ending at Plants to 50 × 6.5 mm. Stem insertion, not decurrent; vaginant laminae 1/2–3/5 the leaf unbranched and sparingly length, ± equal, minor lamina ending on or near margin; branched; axillary hyaline nodules margin crenulate to regularly serrulate but irregularly absent; central strand present. serrate distally, elimbate; costa ending 2–3 cells before Leaves as many as 80 pairs, apex to percurrent, taxifolius-type; laminal cells usually somewhat undulate, oblong, 5 1-stratose, infrequently and irregularly 2-stratose in the

5 5 obtuse to broadly acute, usually 5 5 5 5 5 dorsal and ventral laminae, distinct, smooth, ± plane, 5 bluntly mucronate, to 4 × 1 mm; firm-walled, irregularly quadrate to hexagonal, 10–20 dorsal lamina rounded proximally, µm, 1–5 marginal rows usually thinner with slightly 1 ending at insertion; vaginant laminae /2 the leaf length, thicker walls, forming a lighter marginal band, juxtacostal acute, ± equal, minor lamina ending on or near margin; cells larger, mostly oblong and pellucid; vaginant laminal margin entire but denticulate distally, elimbate; costa cells somewhat larger. Sexual condition dioicous (?); percurrent to ending 2–4 cells before apex, taxifolius- perigonia not seen; perichaetia on short axillary branches, type; laminal cells 1-stratose, distinct, smooth, slightly generally confined to proximal half of stems. Sporophyte bulging, firm-walled, irregularly hexagonal, 10–20 µm, 1 per perichetium. Seta to 25 mm. Capsule theca mostly larger juxtacostally, smaller at margin. Sexual condition ± inclined, ± arcuate, bilaterally symmetric, to 1.5 mm; dioicous; perigonia and perichaetia on short axillary peristome taxifolius-type; operculum to 1.5 mm. branches and main stems. Sporophytes 1–2 per Calyptra cucullate, smooth, to 2.5 mm. Spores 13–22 perichaetium. Seta to 15 mm. Capsule theca slightly µm. inclined, radially symmetric or slightly arcuate, bilaterally Seepage areas, along streams, near waterfalls, symmetric, to 2.5 mm; operculum about as long as theca. meadows, soil, around bases of trees, decaying wood, Calyptra cucullate, smooth, 1.5–1.55 mm. Spores 9–11 dripping limestone and sandstone rocks and boulders; µm. Greenland; Alta., B.C., N.B., Nfld. and Labr. (Nfld.), Calcareous soil, and limestone rocks and boulders N.W.T., N.S., Nunavut, Ont., Que., Sask., Yukon; Ala., along streams and in ravines; Ala., Fla., Ga., Ind., La., Alaska, Ark., Calif., Conn., Del., Fla., Ga., Idaho, Ill., Miss., N.C., S.C., Tex.; Mexico; West Indies; Central Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., America; South America; Asia. Minn., Miss., Mo., Mont., N.J., N.Y., N.C., Ohio, Okla., Oreg., Pa., R.I., Tenn., Tex., Vt., Va., Wash., W.Va., Wis., Wyo.; Europe; Asia; Africa. 340 FISSIDENTACEAE · Fissidens

The usually 1-stratose, distinct, smooth, plane laminal Mexico; West Indies; Central America; Europe; Asia; cells, lighter band of marginal laminal cells, and short Pacific Islands. perichaetial stems in the axils of proximal leaves In contrast to Fissidens adianthoides, F. dubius has distinguish Fissidens adianthoides. The species, smaller, irregularly 2-stratose, obscure laminal cells. nevertheless, can be confused with F. osmundioides, which Subterranean, irregularly globose, multicellular rhizoidal has similar laminal cells without a marginal band of gemmae have been reported for F. dubius as well as F. lighter cells and a serrate leaf apex, but which differs in osmundioides and F. taxifolius in Europe and Japan. Z. having terminal perichaetia and papillose rhizoids. Iwatsuki and T. Suzuki (1982) cited the occurrence of Fissidens dubius, which also has short perichaetial stems dwarf male plants (small perigonial stems located on the in the axils of proximal leaves and often a lighter band leaves of perichaetial plants) in Japanese specimens. of marginal laminal cells, differs from F. adianthoides in its smaller and rather obscure laminal cells that are 6. Fissidens osmundioides Hedwig, Sp. Musc. Frond., consistently irregularly 2-stratose. Fissidens adianthoides 153, plate 40, figs. 7–11. 1801 and F. dubius (as F. cristatus), according to cytological Plants 2–21 × 2–3 mm. Stem evidence presented by L. E. Anderson and V. S. Bryan 5 sparingly branched; axillary (1956), are distantly related. 5 hyaline nodules absent; central 5 5 5 strand present. Leaves in as many

5 5. Fissidens dubius P. Beauvois, Prodr. Aethéogam., 57. 5 5 5 5 as 20 pairs, obovate to lanceolate, 5 5 5 5 5 5 1805 5 5 5 5 5 5 5 5 5 usually widest proximal to the 5 5 5 5 5 5 5 5 5 5 5 5 5 5 Fissidens adianthoides var. 5 5 middle, broadly acute to obtuse, 5 5 semicristatus Grout; F. cristatus often apiculate, 0.7– 2 × 0.3–0.7 5 Mitten; F. cristatus var. winonensis mm; dorsal lamina rounded- (Renauld & Cardot) Grout; truncate proximally, ending at or sometimes before 1 3 5 5 F. decipiens var. winonensis Renauld insertion; vaginant laminae ± /2– /4 the leaf length, 5 5 5 5 5 55 5 5 5 5 5 & Cardot; F. floridanus Lesquereux ± equal, minor lamina ending on or near margin; margin 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 & James crenulate throughout or evenly serrulate distally, elimbate; 5 5 5 5 5 Plants to 25 × 3.5 mm. Stem costa ending 2–14 cells before apex, taxifolius-type; usually branched; axillary hyaline lamina cells 1-stratose, distinct, smooth, bulging, firm- nodules absent; central strand present. Leaves as many walled, ± hexagonal, 10–18 µm. Sexual condition as 25 pairs, often undulate, oblong to lanceolate, obtuse dioicous; perigonia and perichaetia on elongate stems. to acute, often apiculate, to 3.5 × 0.7 mm; dorsal lamina Sporophytes 1 per perichaetium. Seta 2–2.5 mm. Capsule truncate-rounded proximally, ending at insertion, not theca erect, bilaterally symmetric, to 1 mm; peristome taxifolius-type; operculum 1 mm. Calyptra mitrate, decurrent; vaginant laminae 2/3 the leaf length, ± unequal, minor lamina ending near margin; margin crenulate to smooth, 1.5 mm. Spores 16–23 µm. crenulate-serrulate but unevenly serrate at leaf apex, Generally in moist, shaded sites of acidic and basic elimbate; costa ending a few cells before apex to rocks and boulders that are sometimes subject to spray, percurrent, taxifolius-type; laminal cells irregularly 2- soil and humus in seepage areas, meadows, swamps, and stratose in dorsal and ventral laminae, ± obscure, smooth, fens, around bases of trees; Greenland; Alta., B.C., Man., bulging, firm-walled, rounded-hexagonal, 7–10 µm, 3– N.B., Nfld. and Labr. (Nfld.), N.W.T., N.S., Nunavut, 4 rows of marginal cells thinner, walls slightly thicker, Ont., Que., Yukon; Ala., Alaska, Ark., Colo., Ga., Idaho, forming a pale marginal band. Sexual condition dioicous; Ill., Ind., Iowa, Kans., Ky., Maine, Mass., Mich., Minn., perigonia on short axillary branches and elongate stems; Mo., Mont., N.H., N.J., N.Y., N.C., Ohio, Okla., Oreg., perichaetia on short axillary branches, mostly near Pa., Tenn., Vt., Va., Wash., W.Va., Wis.; Europe; Asia. proximal ends of stems. Sporophytes 1 per perchaetium. Fissidens osmundioides is distinguished by its papillose Seta to 11 mm. Capsule theca slightly inclined, slightly rhizoids, evenly crenulate-serrulate leaf margin, broadly arcuate, bilaterally symmetric, to 1.8 mm; peristome acute to obtuse and sometimes apiculate leaf apex, costa taxifolius-type; operculum 1–1.4 mm. Calyptra cucullate, that ends well before the leaf apex, and terminal smooth, 1.8 mm. Spores 13–20 µm. sporophytes. It is most apt to be confused with F. Soil and humus, bases of trees, decaying wood, rocks adianthoides, which has smooth rhizoids, irregularly and boulders in moist, shaded sites; N.B., Nfld. and Labr. serrate leaf apex, a band of lighter marginal cells, and (Nfld.), N.S., Ont., Que.; Ala., Alaska, Ariz., Ark., Calif., sporophytes in the axils of proximal leaves. Conn., Del., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., Maine, Mass., Mich., Minn., Miss., Mo., Neb., N.H., N.Y., N.C., Okla., Pa., S.C., Tenn., Tex., Vt., Va., W.Va., Wis.; Fissidens · FISSIDENTACEAE 341

FISSIDENS

7. Fissidens taxifolius Hedwig, Sp. Musc. Frond., 155, inclined, slightly arcuate, bilaterally symmetric, to 1.5 plate 39, figs. 1–5. 1801 mm; peristome taxifolius-type; operculum to 1 mm. Fissidens clebschii Steere Calyptra cucullate, smooth, to 2 mm. Spores 13–18 µm. Damp, shaded soil, humus, and rocks; N.W.T., N.S., Plants to 11 × 3.5 mm. Stem Ont., P.E.I., Que.; Ala., Ark., Ariz., Calif., Del., D.C., mostly branched; axillary hyaline 5 Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Mass., nodules absent; central strand Mich., Miss., Mo., Nebr., N.H., N.J., N.Y., N.C., Ohio, 5 5 5 5 5 present. Leaves as many as 15 5 5 5 Okla., Oreg., Pa., S.C., Tenn., Tex., Vt., Va., Wash., 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 pairs, often undulate, oblong to 5 5 5 5 5 5 W.Va., Wis.; Mexico; West Indies; Central America; South 5 5 5 5 5 5 5 5 5 5 lanceolate, obtuse to broadly 5 America (Brazil and Chile); Europe; Asia (China, Japan); acute, cuspidate, to 2.7 mm × 0.6 Pacific Islands ( New Zealand). mm; dorsal lamina truncate- Fissidens taxifolius is distinguished by evenly serrulate rounded proximally, ending at insertion, not decurrent; or crenulate-serrulate leaf margin, stout costa ending in 2 vaginant laminae /3 the leaf length, ± equal, minor lamina leaf cusp, conspicuous mammillose cells in the vaginant ending on or near margin; margin evenly serrulate, often laminae, and sporophytes on short branches in the axils crenulate-serrulate on dorsal and ventral laminae, of proximal leaves. It can be confused with F. bushii, but elimbate; costa ending in cuspidate apex, taxifolius-type; that species is smaller, has costa shorter, and cells in the laminal cells 1-stratose, distinct, smooth, bulging, firm- vaginant laminae have small, more or less inconspicuous walled, irregularly hexagonal, 8–11 µm frequently paler papillae in the corners of the walls. Fissidens taxifolius at margin, conspicuously mammillose in vaginant usually occurs on shaded, damp soil or humus, whereas laminae, larger and clearer juxtacostally. Sexual F. bushii is usually found on disturbed soil in woods, condition rhizautoicous; perigonia on short branches along paths, and in road cuts. Fissidens clebschii is proximal to elongate stems; perichaetia on short, considered to be a freakish expression of F. taxifolius proximal, axillary branches. Sporophytes 1 per (R. A. Pursell 2003). perichaetium. Seta to 17 mm. Capsule theca slightly 342 FISSIDENTACEAE · Fissidens

8. Fissidens subbasilaris Hedwig, Sp. Musc. Frond., 155, smooth, bulging, firm-walled, rounded-hexagonal, 7–9 plate 39, figs. 6–9. 1801 µm, papillose in cell corners with 2–4 ± inconspicuous Plants to 12 × 1.5–3.5 mm. Stem papillae in vaginant laminae. Sexual condition dioicous; branched; axillary hyaline nodules perigonia and perichaetia gemmiform, axillary, confined absent; central strand present. to proximal parts of stems. Sporophytes 1 per Leaves as many as 28 pairs, perichaetium. Seta to 10 mm. Capsule theca to 1 mm, erect, ± arcuate, bilaterally symmetric, about 1 mm; 5 sometimes ± undulate, oblong, 5

5 5 peristome taxifolius-type; operculum 1 mm. Calyptra 5 5 5 5 5 obtuse-apiculate to acute, to 2.4 5 5 5 5 5 5 5 5 5 5 5 5 cucullate, smooth, 0.6 mm. Spores 14–18 µm. 5 5 5 5 5 5 × 0.3–0.4 mm; dorsal lamina 5 5 5 narrowed proximally, ending Usually on bare or disturbed clayey soil in open and before or at insertion; vaginant in woods, along paths, roadside banks, along streams, ravines, infrequently on rocks, stones, tree bases; N.B., laminae 1/2–2/3 leaf length, acute, ± unequal, minor lamina ending near margin; margin evenly crenulate-serrulate N.S., Ont., Que.; Ala., Ark., Del., D.C., Fla., Ga., Ill., but irregularly serrate distally; costa ending 6–16 cells Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Miss., before apex, covered and obscured above by Mo., N.H., N.Y., N.C., Ohio, Okla., Pa., S.C., Tenn., chlorophyllose cells, taxifolius-type; lamina cells Tex., Vt., Va., W.Va. irregularly 2-stratose, smooth, bulging, firm-walled, Fissidens bushii, named in honor of the collector of irregularly rounded-hexagonal, 7.5–10 µm. Sexual the type, Benjamin Franklin Bush, is most apt to be condition gonioautoicous and cladautoicous; perigonia confused with F. taxifolius. However, plants of F. bushii gemmiform, axillary, and on short branches; perichaetia are usually much smaller, costa shorter, and leaves on short axillary branches near proximal ends of stem. sometimes caducous. Moreover, small papillae restricted Sporophytes 1 per perichaetium. Seta 1.5–5.5 mm. to the corners of cells in vaginant laminae are distinctive. Capsule theca 0.8–2.1 mm, erect, radially symmetric or The species is probably most closely related to the Asiatic nearly so; peristome taxifolius-type; operculum long F. teysmannianus Dozy & Molkenboer, which also has rostrate, 0.6–0.9 mm. Calyptra cucullate, smooth, 1.5 inconspicuous papillae in the corners of vaginant laminal mm. Spores 13–18 µm. cells. Particularly around bases of trees, also rocks, mostly limestone, infrequently decaying wood; Ont., Que.; Ala., 10. Fissidens aphelotaxifolius Pursell, Bull. Torrey Bot. Ark., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Club 103: 35, figs. 1–15. 1976 Md., Mass., Mich., Miss., Mo., N.H., N.Y., N.C., Ohio, Plants to 17 × 2–3 mm. Stem Okla., Pa., S.C., Tenn., Tex., Va., W.Va., Wis.; Mexico branched; axillary hyaline nodules (San Luis Potosí, Tamaulipas). absent; central strand present. Fissidens subbasilaris is distinguished, even in the field, Leaves as many as 20 pairs, lorate by a costa obscured by chlorophyllose cells distally, and 5 to lanceolate, acute to rounded, 5 short perichaetial branches in the axils of proximal leaves. 5 apiculate, to 2.35 × 0.35–0.65 The plants are typically dark-green and often tinged with 5 mm; dorsal lamina usually red. rounded proximally, ending at insertion, sometimes ending before 9. Fissidens bushii (Cardot & Thériot) Cardot & insertion or slightly decurrent; vaginant laminae 1/2 leaf Thériot, Bot. Gaz. 37: 365. 1904 length, ± equal, minor lamina ending on or near margin; Fissidens subbasilaris var. bushii margin mostly crenulate on dorsal and ventral laminae, Cardot & Thériot mostly serrulate on vaginant laminae and distally, elimbate; costa variable in length, even on same plant, Plants to 13 × 2–2.5 mm. Stem excurrent into apiculus to ending several cells before apex, branched; axillary hyaline nodules taxifolius-type; lamina cells 1-stratose, distinct, smooth, 5 5 5 5 weak; central strand weak. Leaves 5 5 slightly bulging, firm-walled, quadrate to irregularly 5 5 5 5 5 5 5 5 5 55 as many as 20 pairs, oblong to 5 5 5 5 5 5 hexagonal, 6–15 µm, somewhat larger justacostally, 5 5 5 5 5 5 5 5 5 lanceolate, obtuse-apiculate to 5 marginal row thinner, paler. Sexual condition dioicous(?); acute-apiculate, to 2 × 0.5 mm; perigonia unknown; perichaetia on short proximal stems dorsal lamina rounded proximally, and axillary in proximal leaves. Sporophytes, calyptra, ending at insertion, not decurrent; vaginant laminae and spores not known. 2 ± /3 leaf length, ± equal, minor lamina ending on or near Wet soil, humus, and rocks along streams, near margin; margin crenulate-serrulate, more strongly waterfalls, in damp or wet crevices of cliffs; B.C.; Calif., serrulate on vaginant laminae; costa ending 1–2 cells Oreg., Wash. before apex or ending in apiculus, taxifolius-type; laminal Fissidens aphelotaxifolius can be confused with F. cells irregularly 2-stratose in dorsal and ventral laminae, taxifolius but is best distinguished by its smooth and Fissidens · FISSIDENTACEAE 343 slightly bulging laminal cells, distinct from the rostrate, about 1 mm long,” and Iwatsuki and Suzuki conspicuously mammillose cells in the ventral laminae reported that the calyptra is “cucullate, about 1.6 mm of the F. taxifolius. Moreover, the plants tend to be long, smooth.” smaller and leaf apex more coarsely serrulate than in F. taxifolius. Vegetative propagation of F. aphelotaxifolius 12. Fissidens fontanus (Bachelot de la Pylaie) Steudel, is apparently by abundant branched, chlorophyllose Nomencl. Bot. 2: 166. 1824 filaments. Skitophyllum fontanum Bachelot de la Pylaie, J. Bot. Agric. 4: 158, plate 11. Fissidens grandifrons Bridel, Muscol. Recent., suppl. 34, fig. 2. 1815; Octodiceras 1: 170. 1806 julianum var. ohioense Emig; Pachyfissidens grandifrons (Bridel) 5 Fissidens debilis Schwägrichen; 5 5 5 5 5 5 Limpricht 5 5 5 F. julianus (Savi) Schimper 5 5 55 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 5 Plants to 100 × 3.5 mm wide. 5 5 5 Plants to 120 × 6 mm. Stem 5 5 Stem usually profusely branched; 5 usually profusely branched; 5 5

5 5 axillary hyaline nodules present; axillary hyaline nodules absent; 5 5 5 5 5 5

5 5 5 central strand absent. Leaves in central strand absent. Leaves in numerous pairs, 5 5 5 5 5 5 5 as many as 60 or more pairs, lanceolate to linear-lanceolate, frequently somewhat lanceolate, obtuse to rounded, to falcate, acute, to 7 × 0.6 mm; dorsal lamina narrowed 3 × 0.5 mm; dorsal lamina proximally, usually ending before insertion; vaginant narrowed proximally, ending at insertion; vaginant laminae 1/3–1/2 the leaf length, unequal, minor lamina laminae 1/2–2/3 leaf length, acute, equal; margin ± entire usually rounded and free distally or narrowed and ending to crenulate, elimbate; costa usually difficult to discern, on or near costa; margin ± entire, elimbate; costa ending ending a few cells before apex, variable in structure, 15–35 cells before apex, bryoides-type; laminal cells basically taxifolius-type; lamina cells 1- to 4-stratose at usually 1-stratose, sometimes 2-stratose juxtacostally, leaf margin, 2- to pluristratose in interior of dorsal and quadrate to short-oblong to hexagonal, smooth, slightly ventral laminae, 1- to 4-stratose in vaginant laminae, bulging, ± firm-walled, 15–23 × 10–18 µm in dorsal and smooth, ± plain, quadrate to hexagonal, 7–13 µm long. ventral laminae, juxtacostal cells largest. Sexual condition Sexual condition dioicous (?); perigonia not seen; gonioautoicous and cladautoicous; perigonia and perichaetia on short axillary branches in medial leaves. perichaetia on short axillary branches, 1–5 per leaf axil, Seta 13–19 mm. Capsule theca slightly arcuate, bilaterally sometimes on elongate, axillary branches. Sporophytes symmetric, astomatose, exothecial cells quadrate to 1–5 per leaf axil, inconspicuous. Seta 0.5–0.6 mm. oblong, vertical walls thicker than horizontal walls, 1.5– Capsule theca 0.5–0.6 mm, erect, radially symmetric; 2 mm; peristome taxifolius-type. Spores 20–23 µm. peristome anomalous, irregularly divided, ± incomplete, Submerged in rapidly running water in calcareous sites; often truncate, papillose; operculum as long as seta. Alta., B.C., Ont.; Ala., Alaska, Ariz., Ark., Calif., Idaho, Calyptra mitrate, smooth. Spores 18–27 µm. Ill., Ky., Mich., Mo., Mont., N.Y., Oreg., Tenn., Utah, Attached to various substrata in stagnant and flowing Va., Wash., Wyo.; Mexico; Central America; Europe; water, and in coastal estuaries; B.C., Ont.; Ala., Ariz., Asia. Ark., Calif., Conn., Fla., Ga., Idaho, Ill., Ind., Iowa, Kans., Fissidens grandifrons is the only species in the flora Ky., La., Maine, Mass., Mich., Minn., Miss., Mo., Mont., area with pluristratose laminal cells. It is a robust aquatic N.J., N.Mex., N.Y., N.C., Ohio, Okla., Oreg., Pa., R.I., species, usually coarse to the touch. The plants are often S.C., Tenn., Tex., Va., Wash., W.Va., Wis.; Mexico; West brown-black, the result of deposition of organic matter. Indies; Central America; Europe; Africa. Reproduction in North America, where sporophytes have Fissidens fontanus and F. hallianus are aquatic species never been found, is by vegetative means. According to usually found in stagnant or slow moving water, but at E. J. Hill (1902), multiplication is by small, radiculose times emergent because of fluctuating water levels branches that are easily detached in the rapidly running (H. A. Crum and L. E. Anderson 1981; P. G. Davison streams. Although the gametophyte of F. grandifrons is and D. E. Wujek 1999). Plants of both species are usually specialized to an aquatic habitat (thick, lanceolate leaves profusely branched, delicate, and feathery in appearance and long archegonia; Z. Iwatsuki and T. Suzuki 1982; with leaves often 10 times or more as long as wide. Often R. A. Pursell and B. H. Allen 1994), the species has plants are encrusted with diatoms. Stems and leaves retained a distinctly terrestrial type of sporophyte. The might also appear black due to deposition of organic description of the sporophyte given here is based on three matter. When dry the leaves are unusually fragile so that specimens: Lai 8699 (NY) and Lin 12831 (NICH) from when being prepared for herbarium storage it is best to Taiwan; and Higuchi 20161 (NICH) from Pakistan. float plants onto sheets prior to drying. A. J. Grout (1943) stated that the operculum is “conic-