BFNA Title: Dichelyma
Author: B. Allen
Date: January 23, 2010
Edit Level: R
Version: 1

Bryophyte Flora of North America, Provisional Publication
Missouri Botanical Garden

BFNA Web site: http://www.mobot.org/plantscience/BFNA/bfnamenu.htm

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2. DICHELYMA Myrin, Kongl. Vetensk. Acad. Handl. 1832: 273. 1833 * [Greek dicha, in two, and elyma, veil, alluding to large dimidate or cucullate calyptra of the genus]

 

Plants slender to robust, glossy, seasonally inundated. Stems prostrate or pendent, irregularly branched; paraphyllia absent; pseudoparaphyllia absent; axillary hairs 100--300 \um; rhizoids from initials adaxial to the leaf insertions, dark-red, not or irregularly branched. Leaves 3-ranked, distant or crowded, keeled and conduplicate, lanceolate to linear-lanceolate, obtuse, acute or filiform-acuminate; margins entire or obscurely serrulate proximally, serrate to serrulate distally; medial leaf cells linear to linear-rhomboidal; alar cells firm-walled, quadrate or rectangular, not or slightly enlarged; costa subpercurrent, percurrent, excurrent to long-excurrent. Sexual condition dioicous; perigonia gemmate, lateral, in leaf axils; perichaetial leaves elongate, ecostate, sheathing the setae. Seta short or long. Capsule immersed, laterally emergent, emergent or exserted, oval, oval-oblong, subcylindric or cylindric, stomata absent; operculum conic, acute to obliquely rostrate; exostome teeth inserted, linear, trabeculae widely spaced, yellow, orange, or red, spiculose-papillose, perforated along medial line; endostome segments linear, red to brownish-orange, papillose, joined by lateral bars only distally (trellis imperfect) or throughout (trellis perfect). Calyptra long-cucullate, covering the capsule and often clasping the base of the seta when young. Spores smooth or minutely papillose, spheric.

 

Species 5 (4 in flora): North America, Europe, Asia.

 

Dichelyma is a North Temperate genus of five species, four of which occur in North America. Although it is often considered an aquatic moss, Dichelyma is a semi-aquatic genus found along streams, brooks, lakes, ponds, and boggy depressions in the woods on tree and shrub trunks, roots, and rocks or boulders where they are submerged only during periods of flood or high water. Distinctive gametophytic features of the genus include its long, narrow, keeled-conduplicate leaves with strong, single costae, and weakly developed, not or scarcely bulging alar cells. The keeled-conduplicate leaves of Dichelyma lie flat on one side, and, when measuring leaf width it is necessary to double the measurement. Dichelyma has long setae as well as long, sheathing perichaetial leaves; as a result the capsules are typically immersed, emergent, or shortly exserted. The calyptrae in Dichelyma are much longer than those of Fontinalis; they often completely cover the capsules and clasp the setae just below the capsule neck in the same manner as is typical for Calymperes and Timmia.

 

Dichelyma is often confused with species of Drepanocladus (in the broad sense), which can be similar in aspect, size, color, and habitat preference. Many Drepanocladus species, however, have inflated alar cells, and they all differ from Dichelyma in having plane to concave leaves that are often spirally twisted when dry, and not three-ranked. In addition, the sporophytes of Drepanocladus have exserted capsules with stomata, cross-striolate exostome teeth and a typical endostome consisting of a basal membrane, segments and cilia. Blindia, commonly found on rocks and boulders in and along streams, ponds, and lakes has also been confused with Dichelyma. Blindia is acrocarpous and much smaller. In addition, it has well-developed, inflated alar cells, concave leaves, elongated setae, and a single, haplolepidous peristome. Curiously, the aquatic form of Leptodictyum riparium (fo. laxirete) has sometimes been mistaken for Dichelyma. This form of L. riparium is similar in size and aspect to Fontinalis, but differs in having leaves with long, single costae. It differs from Dichelyma in its larger size and in having soft, well-spaced leaves that are concave or plane rather than keeled.

 

1. Capsules emergent or exserted from end of perichaetium; endostome trellis perfect.

2. Leaves at stem and branch tips strongly falcate to circinate; medial stem leaves 0.4--0.8 mm wide........................................................................ 4. Dichelyma uncinatum

2. Leaves at stem and branch tips flexuose-spreading to falcate; medial stem leaves 0.7--1.4 mm wide............................................................................... Dichelyma falcatum

1. Capsules immersed or laterally emergent; endostome trellis incomplete.

3. Leaves linear-lanceolate, setaceous; costae long-excurrent 1. Dichelyma capillaceum

3. Leaves lanceolate, slenderly acute to obtuse; costae subpercurrent to excurrent.........

............................................................................................. 3. Dichelyma pallescens

 

Alternate key to sterile material:

 

1. Leaves of stem and branch tips strongly falcate to circinate............ 4. Dichelyma uncinatum

1. Leaves of stem and branch tips erect-ascending, flexuose-spreading, or falcate.

2. Medial stem leaves 0.7--1.4 mm wide................................. 2. Dichelyma falcatum

2. Medial stem leaves 0.4--0.8 mm wide.

3. Leaves linear-lanceolate, setaceous; costae long-excurrent....... 1. Dichelyma capillaceum

3. Leaves lanceolate, slenderly acute to obtuse; costae subpercurrent to excurrent . . . 3. Dichelyma pallescens

 

1. Dichelyma capillaceum (Withering) Myrin, Kongl. Vetensk. Acad. Handl. 1832: 274. 1833

 

Fontinalis capillacea Withering., Syst. Arr. Brit. Pl (ed. 4) 3: 773. 1801; Neckera capillacea (Withering) Müller. Hal.

 

Plants slender, to 20 cm, green to yellowish green, brownish at base; axillary hairs 100--200 \um, 3--4 cells, basal cell quadrate, brownish, distal 2--3 cells long-cylindrical, hyaline. Leaves weakly three-ranked, linear-lanceolate, filiform-acuminate, 4--7 mm; margins plane; costa long-excurrent, serrulate at apex, occasionally serrulate at base; medial cells 60--120 x 6--8 x \um; alar cells firm-walled, quadrate or rectangular, slightly enlarged. Perichaetial leaves to 7 mm, overtopping the capsule. Seta 3--5 mm. Capsule immersed or laterally emergent, oblong-cylindrical, 1--2 mm; operculum obliquely long-rostrate, 0.5--1 mm; exostome teeth spiculose-papillose; endostome brownish orange, longer than exostome teeth, spiculose-papillose, trellis imperfect. Calyptra 1.5--3 mm. Spores 10--15 \um.

 

Trunks and branches of trees (Acer, Alnus, Carya, Fraxinus, Gleditsia, Liquidambar, Nyssa, Populus, Taxodium, Thuja, Ulmus) and shrubs (Cephalanthus), sticks, and roots or on rocks and boulders along the edges of lakes, ponds, and streams, often in seasonally submerged depressions in woods; low to moderate elevations (0--390 m); Man., N.B., Nfld. and Labr. (Labr.), N.S., Ont., Que.; Ala., Ark., Conn., Del., D.C., Fla., Ga., Ind., La., Maine, Md., Mass., Mich., Miss., Mo., N.H., N.J., N.Y., N.C., Ohio, Okla., Pa., R.I., Tenn., Vt., Va., W.Va., Wis.; Europe.

 

Dichelyma capillaceum, the most common of the species, is equally abundant on bark or rock. It is the most slender species in Dichelyma and has indistinctly keeled, weakly three-ranked leaves with long-excurrent costae. With a hand lens D. falcatum and D. pallescens can be separated from D. capillaceum by their larger size and strongly keeled, distinctly three-ranked, lanceolate leaves. Dichelyma uncinatum, also a slender species, differs in having leaves of stem and branch tips strongly secund to circinate, while those of D. capillaceum are mostly erect or spreading. The sporophytes of D. capillaceum and D. pallescens are more or less identical and the two species are sometimes found growing together. Dichelyma pallescens further differs in having acute to obtuse leaf apices.

There is a Newfoundland collection of Dichelyma capillaceum made by Fowler at Grand Lake, Sept. 18 1879 (NY) that which Ireland annotated as probably an error for Grand Lakes, New Brunswick. Fowler collected mosses mostly in New Brunswick, there is no indication he collected in Newfoundland. Welch (1960) reported D. capillaceum from Manitoba (Hand 528, July 20, 1938, near Rennie); this specimen could not be located.

 

2. Dichelyma falcatum (Hedwig) Myrin, Kongl. Vetensk. Acad. Handl. 1832: 274. 1833

 

Fontinalis falcata Hedwig, Sp. Musc. Frond., 299. 1801

 

Plants medium to robust, to 15 cm, green, yellowish or yellow-brown; axillary hairs 200--300 \um, 5--7 cells, basal 1--2 cell(s) quadrate, brownish, distal 4--5 cells long-cylindrical, hyaline. Leaves strongly three-ranked, lanceolate, acute, acuminate or subulate, 3--5 mm; margins plane or very narrowly recurved, entire proximally, serrulate distally; costa subpercurrent, percurrent to variously excurrent; medial leaf cells 120--200 x 6--8 x \um; alar cells firm-walled, quadrate or rectangular, not or slightly enlarged. Perichaetial leaves to 7 mm, not overtopping the capsule. Seta 10--15 mm. Capsule exserted, oval to oblong-cylindrical, 1--2 mm; operculum obliquely long-rostrate, 0.5--1 mm; exostome teeth yellowish, finely papillose; endostome yellowish, longer than exostome teeth, finely papillose, trellis perfect. Calyptra 3--6 mm. Spores 12--14 \um.

 

Rocks or stones (occasionally tree bases, and roots) in and along brooks, wet depressions, stream banks; low to high elevations (63--3444 m); Alta., B.C., Man., Nfld. and Labr., Ont., Que.; Alaska, Colo., Maine, Mich., Minn., N.H., N.Y., Utah, Vt., Wis., Wyo.; Europe; Asia (Siberia, China).

 

Dichelyma falcatum is the largest species in the genus. Critical features include strongly ranked, usually acute, lanceolate leaves that vary from erect to somewhat falcate at the stem and branch tips; exserted capsules; and perfect endostomial trellises. Although its leaves are about the same length as those of the other species, they are much broader: D. falcatum 0.7--1.4 mm wide; D. capillaceum, D. pallescens, D. uncinatum 0.4--0.8 mm wide. Dichelyma pallescens is often confused with D. falcatum, but that species usually occurs on bark rather than rocks and boulders. It also has narrower leaves with broader, frequently obtuse apices; immersed to emergent capsules; and imperfect endostomial trellises. The leaves of D. falcatum are sometimes long-excurrent, and this has caused it to be confused with D. uncinatum. Both species have exserted capsules with perfect endostomial trellises; D. uncinatum differs from D. falcatum in having leaves that are more slender, and strongly secund to circinate at the stem and branch tips.

 

3. Dichelyma pallescens Bruch & Schimper in Bruch, Schimper & Gümbel, Bryol. Eur. 5: 24.1846

 

Dichelyma obtusulum Kindberg; Neckera leucoclada Müller Hal., Syn. Musc. Frond. 2: 144. 1850

 

Plants slender to medium sized, to 10 cm long, somewhat glossy, green, yellowish or yellow-brown. Axillary hairs 140--200 \um long, 3--6 cells, basal 1 cell quadrate to subrectangular, brownish, upper 2--5 cells long cylindrical to oblong, hyaline. Leaves weakly three-ranked, lanceolate, subulate to acuminate, acute to obtuse, 3--4 mm long;, margins plane, entire below, serrulate above; costa subpercurrent to percurrent; medial leaf cells 100--140 x 5-8 x \um, alar cells firm-walled, quadrate or rectangular, slightly enlarged. Perichaetial leaves up to 7 mm long, overtopping the capsule. Setae 4--7 mm long. Operculum obliquely long-rostrate, 0.5--1 mm long. Capsule emergent, oval to oblong-cylindrical, 1--2 mm long. Exostome teeth reddish, finely papillose, at times perforated along medial line. Endostome reddish, longer than exostome teeth, finely papillose, trellis imperfect. Calyptra 3--4 mm long. Spores 10--15 \um.

 

On tree (Acer, Alnus, Fraxinus, Populus) trunks and bushes (occasionally on rocks) subject to inundation during times of high water; low to medium elevation (40--426 m); N.B., Nfld and Labr. (Nfld.), Ont., Que.; Maine, Mass, Mich., Minn, N.H., N.Y., Pa., Vt., Wis.

 

Dichelyma pallescens is a mostly corticolous species that differs from all other North American Dichelyma species in often having broadly acute to obtuse leaf apices. It is a medium-sized species that is occasionally confused with D. falcatum. Dichelyma flacuatum is usually saxicolous, has much broader leaves (0.7--1.4 vs.0.4--0.8 mm wide), exserted capsules, and perfect endostomial trellises. Dichelyma capillaceum and D. pallescens often occur in mixed collections; both have immersed to laterally emergent capsules with imperfect endostomial trellises. Dichelyma capillaceum differs from D. pallescens in having setaceous leaf apices and long excurrent costae.

 

4. Dichelyma uncinatum Mitten, J. Linn. Soc., Bot. 8: 44. 1864

 

Dichelyma cylindricarpum Austin; D. falcatum var. uncinatum (Mitten) E. Lawton; D. uncinatum var. cylindricarpum (Austin) Cardot

 

Plants slender, to 12 cm, green to yellowish green, brownish at base; axillary hairs 180--220 \um, of 4--5 cells, basal cell quadrate, brownish, distal 3--4 cells long-cylindrical, hyaline. Leaves weakly three-ranked, linear-lanceolate, filiform-acuminate, 4--5 mm; margins plane; costa long-excurrent, serrulate at apex; medial cells, 60--110 x 4--8 x \um; alar cells firm-walled, quadrate or rectangular, not or slightly enlarged. Perichaetial leaves to 7 mm, sheathing the setae, not or rarely overtopping the capsule. Seta 4--12(--20) mm. Capsule emergent or shortly exserted, oblong-cylindric to cylindric, 1--3 mm; operculum conic, 1--1.5 mm; exostome teeth spiculose-papillose; endostome yellowish brown to orange-red, spiculose-papillose, trellis perfect. Calyptra 3--5 mm. Spores 10--17 \um.

 

Tree trunks and branches (Acer, Alnus, Populus, Quercus, Salix, Toxicodendron), roots, shrubs (occasionally rocks), swamps, bottom forests, flood plains, pond margins, frequently submerged at high water; low to high elevation (6--1066 m); B.C., Ont.; Alaska, Calif., Idaho, Mont., Oreg., Wash., Wyo.

 

Dichelyma uncinatum is corticolous (rarely on rock), and differs from other Dichelyma species in having strongly falcate to circinate leaves at tips of the stems and branches. Dichelyma capillaceum is similar to D. uncinatum in size, and both species have slender, linear-lanceolate leaves with setaceous apices and long-excurrent costae. In D. capillaceum the stem and branch tips have erect-spreading to flexuose-spreading and somewhat longer (4--7 vs. 4--5 mm) leaves. In addition D. capillaceum has immersed or laterally emergent capsules and incomplete endostomial trellises. Dichelyma falcata has been confused with D. uncinatum because it sometimes has excurrent costae, and both species have exserted capsules with perfect endostomial trellises. But, D. falcatum, is usually saxicolous and has much broader leaves (0.7--1.4 vs. 0.4--0.8 mm wide) that are flexuose-spreading to falcate at the stem and branch tips. The remarkable record of D. uncinatum from southeastern Ontario (Parry Sound District, Ireland 22206 MO, NY) occurred mixed with a collection of D. falcatum.