BFNA Title: Sciuro-hypnum
Author: M. S. Ignatov 
Date: October 6, 2008
Edit Level: R 
Version: 1

Bryophyte Flora of North America, Provisional Publication
Missouri Botanical Garden
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BRACHYTHECIACEAE -- Sciuro-hypnum  

XX. Sciuro-hypnum (Hampe) Hampe, Linnaea 38: 220. 1874  *  [Latin sciurus, squirrel, and Hypnum, generalized pleurocarpous moss, appearance reminiscent of squirrel tail]

Michael S. Ignatov

Hypnum subg. Sciuro-hypnum Hampe, Flora 50: 76. 1867


Plants small to large, light to deep green, sometimes becoming yellowish, brownish, or rarely brownish red with age. Stems prostrate, ascending or arching, central strand present, loosely to densely terete or rarely complanately foliate, irregularly to sometimes fairly regularly pinnately branched, branches straight or curved, foliage somewhat denser than that of stem and sometimes subcomplanate; axillary hairs 2--3(--5)-celled; juvenile branch leaves acute. Stem leaves loosely arranged to closely imbricate, erect to patent and reflexed, occasionally twisted or falcate-secund, broadly ovate to ovate-lanceolate or deltoid, broadest at 1/10--1/5\x leaf length, acuminate or acute, rounded to base and often conspicuously decurrent or decurrencies inconspicuous, rather short, narrow, and remaining on stem after leaf detaching; slightly to strongly concave, indistinctly plicate to smooth; margin serrate distally to subentire; costa reaching mid leaf to percurrent, ending in a small abaxial spine or spine absent; basal cells near costa undifferentiated, or broader and forming a pellucid zone, or only slightly broader and moderately thick-walled and forming an opaque zone across the leaf base; cells in leaf corners variable in size, pellucid or opaque; mid leaf cells slightly elongate (3--4:1) to linear (10--20:1), thin- to moderately thick-walled, smooth, rarely prorate abaxially (S. starkei). Branch leaves smaller and narrower than stem leaves, with more strongly serrate margins and the costa more often ending in a spine. Sexual condition autoicous, rarely dioicous (S. latifolium and S. hylotapetum), sporophytes rare; perichaetial leaves reflexed. Seta red-brown or sometimes cherry-red, rough or more rarely weakly so to almost smooth. Capsule dark red-brown, slightly inclined to horizontal or somewhat patent, very rarely erect (S. delicatulum), when premature sometimes strongly patent to circinate with operculum turned upward; elongate and curved to shortly ovate and almost not curved or curved only dorsally; annulus separating by fragments; operculum conic to high-conic and occasionally with short beak; peristome xerocastique, perfect (except S. delicatulum with rather low basal membrane and cilia short to absent). Calyptra naked. Spores 9--20 \um.


Species ca. 30 (12 in the flora): all continents, including boreal and temperate zones, alpine to middle elevations in the tropics.


The genus Sciuro-hypnum was segregated from Brachythecium by M. S. Ignatov and S. Huttunen (2002). Previously, species of Sciuro-hypnum were placed in Brachythecium in two sections: sect. Reflexa and sect. Plumosa (V. F. Brotherus 1925). Sciuro-hypnum differs from Brachythecium in the mostly small plant size, the, almost always autoicous sexual condition (except S. latifolium and S. hylotapetum), and rough setae. Among species of Brachythecium, the combination of autoicous sexual condition and a rough seta is rare in North America and is known only in B. rutabulum, B. bolanderi, and B. campestre.


SELECTED REFERENCES Crum, H. A. and L. E. Anderson 1981. Mosses of Eastern North America. 2 vols. New York. Lawton, E. 1971. Moss Flora of the Pacific Northwest. Hattori Botanical Laboratory, Nichinan.


1.         Costa reaching 0.8\x leaf length to percurrent.

2.         Basal cells relatively small, quadrate to sub-quadrate, forming an opaque area across leaf base.

3.          Leaves straight; widespread . . . 2. Sciuro-hypnum populeum

3.          Leaves falcate secund or reflexed, with acumens turned to all sides or secund; Alaska . . . 3. Sciuro-hypnum uncinifolium

2.         Basal cells near costa somewhat wider and shorter than mid leaf cells, but not clearly differentiated; basal cells in leaf corners more or less enlarged and usually pellucid, although sometimes may look opaque due to collapsed cytoplasm, in this case the opaque area is restricted to leaf corners, reaching about half distance to costa.

4.          Mid leaf cells 3--6:1.

5.          Stem leaves long-acuminate from an ovate to deltoid base, broadly and long-decurrent; widespread  . . . 6. Sciuro-hypnum reflexum (in part)

5.          Stem leaves acute or short-acuminate from a broadly ovate to ovate-triangular base, narrowly and short-decurrent; Arctic. . . 5. Sciuro-hypnum glaciale (in part)

4.          Mid leaf cells (6--)7--15:1.

6.          Plants soft; branching irregularly pinnate, rarely regularly pinnate; branch leaves appressed to stem proximally, long-acuminate; distal laminal cells of branch leaves smooth; Pacific region . . . 6. Sciuro-hypnum reflexum  (in part)

6.          Plants rather rigid; branching regularly pinnate, at least in part; branch leaves spreading, usually fairly gradually tapered to apex, rarely short-acuminate; distal laminal cells of branch leaves prorate; Atlantic region . . 8. Sciuro-hypnum starkei

1.         Costa reaching 0.2--0.8\x leaf length.

7.         Plants large, light green to whitish, stem leaves 2.2--3.7 x 1.3--2 mm; dioicous, sporophytes rare; montane forests of western North America . . . 12. Sciuro-hypnum hylotapetum

7.         Plants small to moderately robust, variously green, yellow, or brownish, occasionally reddish; stem leaf in the largest species 1.4--2.4 x 0.9--1.5 mm; most species autoicous, sporophytes usually common; widespread.

8.          Alar cells thin-walled, forming a more or less conspicuous pellucid group in the leaf corners or adjacent to decurrency.

9.          Leaves entire; plants usually pale green to yellow-green; dioicous; Arctic-alpine or forests on wet rocks or in peatlands . . . 9. Sciuro-hypnum latifolium

9.          Leaves serrate to serrulate; plants darker green; autoicous; forests, rarely in Arctic.

10.        Leaves loosely arranged, erecto-patent to patent, slightly concave, gradually acuminate to narrowly acute from broadly ovate base; widespread in boreal and hemiboreal forests of eastern North America, rarely in Rocky Mts. . . . 11. Sciuro-hypnum curtum

10.        Leaves closely imbricate and strongly concave, more or less strongly rounded to the broadly acute apex; rare in Arctic Alaska . . . 10. Sciuro-hypnum ornellanum

8.          Alar cells moderately thick-walled, opaque, not forming a pellucid group.

11.        Leaves lanceolate to ovate-lanceolate.

12.        Leaves narrowly lanceolate, 3--4:1; small alar cells forming an elongate group along the margin, but not reaching the costa; capsule erect or suberect; Utah . . . . 4. S. delicatulum

12.        Leaves lanceolate to ovate-lanceolate, 1.5--2.5:1; small cells differentiated across the entire leaf base (only rarely in the broadest leaves do small cells not reach the costa); capsule inclined to horizontal; widespread . . . 1. Sciuro-hypnum plumosum

11.        Leaves ovate to broadly ovate-triangular.

13.        Leaves acute; mid leaf cells 3--6:1; Arctic to subarctic . . . 5. Sciuro-hypnum glaciale (in part)

13.        Leaves acuminate; mid leaf cells 4--10:1; widespread in mountains of the West . . . 7. Sciuro-hypnum oedipodium


1. Sciuro-hypnum plumosum (Hedwig) Ignatov & Huttunen, Arctoa 11: 270. 2002 [2003]


Hypnum plumosum Hedwig, Sp. Musc. Frond., 257. 1801; Brachythecium plumosum (Hedwig) Schimper; Eurhynchium semiasperum Müller Hal. & Kindberg


Plants small to medium-sized, in rather dense or loose tufts, deep green, brownish green to reddish golden, sometimes with reddish (ferruginous) spots on some of leaves. Stems prostrate, to 5 cm, straight to slightly curved, branches to 6 mm, straight to curved, terete foliate. Stem leaves erect-appressed to erect, densely to moderately densely imbricate, 1.4--2 x 0.4--1 mm, ovate-lanceolate to ovate, concave, shortly acuminate, rather narrowly decurrent, straight or somewhat falcate, smooth, costa to 0.35--0.65\x leaf length, broad below and much narrowing in its lower portion, ending smoothly or in a small indistinct spine; margin serrulate, plane or recurved just beyond leaf insertion; basal cells in 3--7 rows across the base, short-ovate, ca. 10 \um wide, thick-walled, forming opaque area across the base; alar cells similar to juxtacostal cells or slightly larger, in broader leaves occasionally enlarged to 15 \um wide in leaf corners; laminal cells elongate, 30-75(--90) x 5.5--9 \um, often somewhat flexuose, smooth. Branch leaves smaller, margin more strongly serrate. Sexual condition autoicous; sporophytes frequent. Seta cherry red, 12--20(--24) mm, rough, but sometimes weakly so. Capsule reddish brown, slightly to moderately inclined, ovate, slightly curved dorsally, 1.3--2 mm long; operculum high conic, sharp. Spores 13--19 \um.


Rocks along creeks, often temporarily submerged, wet, shaded rock cliff and rock outcrops, occasionally wet soil, more rarely bark of tree bases; 0--3050 m; B.C., Man., N.B., Nfld. and Labr. (Nfld., Labr.), N.W.T., N.S., Ont.; Ala., Alaska, Ariz., Ark., Calif., Colo., Conn., Del., D.C., Fla., Ga., Idaho, Ill., Ind., Iowa, Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Mont., N.H., N.J., N.Y., N.C., Ohio, Oreg., Pa., R.I., S.C., Tenn., Vt., Va., Wash., W.Va., Wis., Wyo; Mexico; Central America; South America; Eurasia; Africa; Atlantic Islands; Pacific Islands; Australia; Antarctic Islands.


Sciuro-hypnum plumosum is widespread in North America but is absent in the central southern states where conditions are too dry or where rocky substrates are rare. Sciuro-hypnum plumosum is the most widespread species of the Brachytheciaceae, occurring from polar areas (e.g., in Chukotka) to tropical mountains in Hawaii and Papua New Guinea. In some areas of the world (e.g., in Russian Far East and China), this species is common in epiphytic and epixylic habitats, whereas in the rest of the world it grows mostly on permanently seeping rocks usually beside small creeks and streams. Interestingly, in North America, it also occasionally occurs on tree trunks in the eastern states, mainly in New England, but not in the more southern states despite these being more similar to China in flora and climate. This species is variable especially in leaf width and degree of falcation. Plants from dryer habitats (especially trees) have narrower leaves, while northern populations from semipermanently wet rocks sometimes have strongly falcate leaves. The transition between these extremes does not allow for satisfactory segregation of these forms. Although Sciuro-hypnum plumosum is extremely variable, it is usually easy to recognize with stereomicroscope or hand lens. The often variegated color patterning with ferruginacous or even cherry-reddish strips is characteristic. However, in evenly colored plants, the leaves are very strict and very broadly channeled; the narrowing of the costa in the proximal third of leaf and the opaque cells across the leaf base are also characteristic . Brachythecium acuminatum may sometimes be confused with S. plumosum, as both have more or less isodiametric cells across the leaf base; however, the former species has larger and more transparent basal cells and its leaves usually have distinct submarginal plicae. In addition, rough setae are frequently present in S. plumosum (the setae are smooth in B. acuminatum, but uncommon, as the species is dioicous). Sciuro-hypnum oedipodium also may have an extensive opaque area in leaf corners, but never across whole leaf base. In some cases, especially in wetter habitats, cells in the leaf corners of S. plumosum can be enlarged and pellucid, but, in this case, small opaque cells remain between them and mid leaf cells.


2. Sciuro-hypnum populeum (Hedwig) Ignatov & Huttunen, Arctoa 11: 270. 2002 [2003]


Hypnum populeum Hedwig, Sp. Musc. Frond., 270, plate 70, figs. 1--6. 1801; Brachythecium populeum (Hedwig) Schimper


Plants small to medium-sized, in rather dense or loose tufts, green, yellowish green to brownish yellow. Stems prostrate, to 5 cm, straight to slightly flexuose, branches to 7 mm, straight to slightly curved, terete-foliate. Stem leaves erect-appressed to erect, closely imbricate, 1.2--1.9 x 0.4--0.6 mm, ovate-lanceolate, gradually tapered to apex, shortly acuminate, moderately broadly decurrent, straight, smooth or indistinctly plicate, costa to 0.8--1\x leaf length, geniculate just proximal to acumen; margin serrulate to subentire, plane or recurved in places (more commonly proximally); basal cells subquadrate to quadrate in about 5 rows, relatively small, 7--12(--15) \um wide, thick-walled, forming an opaque area across leaf base; laminal cells 25--80 x 5--8 \um, elongate or sometimes rhomboidal, smooth. Branch leaves smaller, costa somewhat serrate dorsally, margin more strongly serrate. Sexual condition autoicous; sporophytes frequent. Seta reddish brown, 8--15 mm, rough, sometimes slightly so. Capsule reddish brown, slightly to moderately inclined, ovate, slightly curved dorsally, 1--2 mm long; operculum conic. Spores 12--16 \um.


Rocks, especially granitic boulders, but sometimes also limestone, sometimes on concrete, occasionally on trunks of deciduous trees, soil, usually exposed or moderately shaded and rather dry habitats; 10--500(--2000) m; Greenland; B.C., Man., N.B., Nfld. and Labr, N.S., Ont., P.E.I., Que.; Alaska, Colo., Conn., Del., Iowa, Maine, Md., Mass., Mich., Minn., N.H., N.J., N.Y., N.C., Ohio, Pa., Tenn., Vt., Va., W.Va., Wis.; Europe; Asia; Atlantic Islands.


Sciuro-hypnum populeum is widespread in the boreal and north-temperate Eastern North America south to North Carolina. There are only few stations in western North America. This is usually a lowland species, and the only exception is the population in Colorado at 2000 m (Boulder Co., Bear Mt., W. A. Weber & R. C. Wittmann, B-112127, CO). H. A. Crum and L. E. Anderson (1981) noticed that, unlike the situation in Europe, this species does not grow on tree trunks in North America, which is generally true although it has occasionally been collected on tree bases in forests. Sciuro-hypnum populeum can be recognized by the combination of percurrent costa with opaque basal cells, unique among North American Brachytheciaceae. Sometimes it has been confused with Homalothecium species with costae masked by their characteristic laminal plications, and appearing percurrent; Sciuro-hypnum has only slightly plicate leaves. Brachythecium acuminatum and Sciuro-hypnum plumosum are similar to S. populeum having short and more or less uniform cells across the leaf base, but the costa in these species disappears well below the apex. Sciuro-hypnum populeum may develop rather broad stem leaves with bigger basal cells in relatively wet conditions, as has S. reflexum. The more gradual tapering of the leaves is, however, diagnostic.


3. Sciuro-hypnum uncinifolium (Brotherus & Paris) Ochyra & Żarnowiec, Biodiversity of Poland 3: 175. 2003


Brachythecium uncinifolium Brotherus & Paris, Rev. Bryol. 31: 64. 1904; Cratoneurella uncinifolia (Brotherus & Paris) H. Robinson


Plants small, in dense or loose tufts, green to yellow-brown. Stems to 3.5 cm, prostrate, flexuose, terete foliate, irregularly pinnate branching, branches to 4 mm, straight to slightly curved, terete-foliate. Stem leaves closely imbricate, with appressed basal portions and wide spreading to reflexed or otherwise strongly falcate-secund acumens, 0.8--1.1 x 0.4--0.5 mm, ovate or triangular-ovate, gradually or abruptly narrowly acuminate, moderately to distinctly constricted to base, not plicate, margins serrulate, plane or recurved proximal to the broadest point of leaf; basal cells subquadrate and shortly ovate in 7--10 rows, relatively small, 6--12(--15) x 6--10(--15) \um, thick-walled, forming extensive opaque area across the base; laminal cells 30--50 x 5--8 \um, elongate, smooth. Branch leaves similar to stem leaves. Sexual condition autoicous; but sporophytes rare, unknown in North America.


Boulders on stream banks, rocks in Populus stand, dry open earth on cliff ledge, humid cliff; 20 m; Alaska; Asia (China, Japan, Russia in Kuril Islands and Kamchatka).


Sciuro-hypnum uncinifolium for long has been considered a Japanese endemic, but recently it was found in Russia in Kamchatka and in Kuril Islands (I. V. Czernyadjeva and M. S. Ignatov 2006; V. Ya. Cherdantseva et al. 2006) and also in islands near Alaska and in the Alaskan peninsula (M. S. Ignatov 2007), so it is to be expected in the Aleutian Islands. Sciuro-hypnum uncinifolium is easily recognized by narrow shoots with appressed leaves, and leaves rigidly reflexed, with squarrose to secund acumens. This species combines the characters of S. reflexum (leaf shape and reflexed acumen) and S. populeum (opaque cells across the leaf base). From molecular phylogenetic analyses of M. S. Ignatov and I. A. Milyutia (2007b) and I. Draper and L. Hedenäs (in press), it is more closely related to the latter species. Despite its autoicous condition, sporophytes are rare in this species.



4. Sciuro-hypnum delicatulum (Flowers) Ignatov, unpublished.


Brachythecium delicatulum Flowers, Bryologist 76: 287. 1973


Plants moderately small to medium sized, in loose or moderately dense tufts, green to yellowish green. Stems to 5 cm, prostrate, terete foliate, irregularly to rather regularly pinnate branched, branches to 10(--15) mm, straight to flexuose, terete or subcomplanately foliate. Stem leaves densely to loosely arranged, often loosely arranged at shoot ends, falcate-secund from an erect base, 1.4--2.5 x 0.35--0.7(--0.9) mm, gradually or abruptly acuminate from an ovate or ovate-lanceolate base, acumen often falcate or flexuose; slightly to moderately plicate, rarely smooth, margin serrulate to base, rarely subentire, plane or recurved in places (more commonly proximally); costa reaching 0.5--0.75\x leaf length, ending in a small abaxial spine; juxtacostal basal cells shorter, to 8--10 \um wide, indistinctly delimited; in leaf corners subquadrate, forming a triangular, fairly distinct group of 10--25 x 8--15 \um cells extending 8--10 cells along the margin and 5--8 cells along the leaf base; laminal cells linear, 50--90 x 45--10 \um. Branch leaves smaller, narrower, variably lanceolate to linear, in the latter case alar cells extending along margin to the broadest point of leaf thus forming group of 12 x 3--4 cells. Sexual condition autoicous. Seta reddish, 10--15 mm, smooth or slightly rough above. Capsule reddish, inclined, sometimes only slightly and then almost erect, ovate, 10--20 mm; peristome in more short and straight capsules with somewhat reduced endostome where basal membrane is only 1/3 of endostome and cilia short to absent. Spores 10--15 \um.


Soil, damp to rather dry rocks, in shaded places, especially under overhanging rocks and exposed tree roots; 1700--1800 m; Utah.


The type series of Sciuro-hypnum delicatulum also includes specimens from 2550 m elev., but these are B. velutinum. Sciuro-hypnum delicatulum is a local endemic in Utah, from City Creek Canyon in Salt Lake County (S. Flowers 1973). The species is characterized by very narrow leaves, rather numerous alar cells, and somewhat reduced peristome. Its affinity as well as generic placement needs further study.


5. Sciuro-hypnum glaciale (Schimper) Ignatov & Huttunen, Arctoa 11: 270. 2002 [2003]


Brachythecium glaciale Schimper, Bryol. Eur. 6: 15, plate 542. 1853


Plants medium-sized, in loose tufts, green to yellowish- or greyish green. Stems to 6 cm, prostrate or arching, terete foliate, irregularly branching, branches to 8 mm, straight to curved, terete foliate. Stem leaves closely imbricate, 1--1.5(--1.8) x 0.6-0.9(--1.1) mm, ovate-triangular, broadest at 1/7--1/5\x leaf length, gradually tapered towards apex, acute or shortly acuminate, rounded to base, short-decurrent, concave, not or slightly plicate, margin plane distally, recurved proximally, serrulate almost throughout; costa to 0.4--0.7(--1)\x leaf length, weak to strong in different populations, ending without an abaxial spine; juxtacostal basal cells slightly shorter than laminal cells but not conspicuously differentiated, 8--10 \um wide, with cell walls about the same thickness as with laminal cells, cells in leaf corners subquadrate and short rectangular, ca. 15 x 10 \um, forming conspicuous opaque or weakly pellucid group reaching ca. 1/2 distance to costa; mid leaf cells elongate, 30--70 x 6--11\um, smooth. Branch leaves smaller, ovate-lanceolate to lanceolate, more strongly serrate. Sexual condition autoicous, sporophytes infrequent. Seta orange-brown, 10--17 mm, rough. Capsule orange-brown, inclined to horizontal, ovate, curved dorsally, to 1.8 mm, operculum high-conic. Spores 12--16 \um.


Soil, rocks, especially near glaciers, otherwise open, cold habitats; 0 m; Greenland; Que.; n Europe; n Asia.


Sciuro-hypnum glaciale has a wide distribution globally, but is probably locally common only in Scandinavia. In North America it is confirmed in Greenland and Newfoundland, but probably occurs also in other regions of the North American Arctic. The species can be recognized by broadly ovate-triangular and concave leaves forming closely imbricate foliage of plants. The costa is variable, ending at mid leaf to almost percurrent. The species is similar to S. oedipodium and S. reflexum, but S. oedipodium has acuminate not acute leaves and usually longer laminal cells; the latter species has less concave leaves with longer acumens and conspicuous decurrencies.


6. Sciuro-hypnum reflexum (Starke) Ignatov & Huttunen, Arctoa 11: 270. 2002 [2003]


Hypnum reflexum Starke, Bot. Taschenb., 306. 1807; Brachythecium reflexum (Starke) Schimper; B. reflexum var. pacificum Renauld & Cardot; B. bestii Grout; B. starkii var. pacificum (Renauld & Cardot) E. Lawton; Eurhynchium pacificum (Renauld & Cardot) Kindberg


Plants small to medium-sized, in dense or loose tufts, green to dark or brownish green, occasionally light green. Stems to 5(--8) cm, prostrate to arching, terete foliate, irregularly to fairly regularly pinnate branched; branches to 8 mm, often curved. Stem leaves more or less loosely arranged, occasionally imbricate, appressed to stem at their bases, spreading to reflexed distally, 1--1.5(--2) x 0.5--0.9(--1.2) mm, ovate or ovate-triangular, broadest at ca. 1/7\x leaf length, gradually to abruptly acuminate, concave, smooth or indistinctly plicate; margin serrulate throughout, sometimes almost entire, plane or recurved proximally; costa ending in acumen, often obscure in distal region, ending without an abaxial spine; juxtacostal basal cells almost undifferentiated, only slightly and gradually shorter than distal cells; cells distal to decurrency enlarged, subquadrate, short-rectangular, 15--30 x 12--20 \um wide, cell walls as thick as laminal cells, forming a pellucid or opaque (by collapsed cytoplasm) area, occupying distal part of decurrency, extending along margin to broadest point of leaf, and usually reaching more than half distance to costa, being composed of ca. 15 x 15 cells; laminal cells 25--70(--90) x 6--10(--12) \um, short to moderately elongate, smooth. Branch leaves usually closely imbricate, narrowly ovate to ovate-lanceolate, margin more strongly serrate. Sexual condition autoicous, rarely paroicous. Seta dark red-brown, 8--15 mm, rough. Capsule dark red-brown or occasionally rather light brown, inclined to horizontal, shortly ovate to occasionally ovate-cylindric, and if longer then curved, 1--1.5 mm. Spores (10--)12--17 \um.


Bases of trees, especially hardwoods, occasionally on conifers; also on wood and litter in boreal and hemiboreal forests; 0--1300 m; Greenland; B.C., Man., N.B., Nfld. and Labr., N.S., Ont., P.E.I., Que., Sask.; Alaska, Idaho, Maine, Md., Mass., Mich., Minn., Mont., Oreg., N.H., N.J., N.Y., Pa., Vt., Va., Wash.; Wis.; Europe; Asia; Atlantic Islands; Pacific Islands.


Sciuro-hypnum reflexum is characterized by the costa vanishing in the acumen and deltoid, broadly decurrent leaves. It is not especially variable in eastern North America, where it is found most commonly on tree bases and fresh logs in forests. Sporophytes are frequent. It is easily recognized by rather small plants, curved branches and numerous shortly ovate capsules on rough setae. The situation in the Western North America is more complicated: “typical” plants as described above for eastern North America occur in Alaska and British Columbia, but there are also plants described as “B. reflexum var. pacificum Renauld & Cardot” in the mountains of Idaho and Montana where typical S. reflexum appears absent. This “var. pacificum differs from typical S. reflexum mainly in longer laminal cells and longer stems with distantly spaced branches. However, the very gradual transition to typical S. reflexum precludes the segregation of var. pacificum as a separate taxon at the moment. Superficially var. pacificum is somewhat similar to weakly developed S. oedipodium, and without examination under the compound lens lens they can be confused because the costa, although vanishing in the acumen, is weak and not differentiated in color.


7. Sciuro-hypnum oedipodium (Mitten) Ignatov & Huttunen, Arctoa 11: 270. 2002 [2003]


Hypnum oedipodium Mitten, J. Proc. Linn. Soc., Bot. 8: 35. 1864; Brachythecium collinum var. holzingeri Grout; B. holzingeri (Grout) Grout; B. oedipodium (Mitten) A. Jaeger


Plants medium-sized, rarely rather robust or small, in rather loose tufts, light green, often stramineous. Stems to 5 cm, ascending, arching, often curved distally, terete foliate, irregularly pinnate; branches to 7 mm, often curved, terete foliate. Stem leaves erect, imbricate or sometimes erectopatent, (1.2--)1.6--2.2 x (0.5--)0.7--1.1 mm, ovate (broadest at 1/5--1/6\x leaf length), acuminate, rounded to base, concave, not or slightly plicate, decurrency of several cells, broad and conspicuous; margins plane or often recurved below the broadest part of leaf, serrulate; costa moderately weak, reaching 0.55--0.75\x leaf length, ending without an abaxial spine; juxtacostal basal cells short-rectangular to ovate in ca. 3 rows, usually with oblique transverse walls, cells in leaf corners broader, subquadrate to short-rectangular, with transverse walls perpendicular to their length, 15--25 x 12--16 \um, moderately thick-walled, appearing opaque because of collapsed cytoplasm, forming an extensive alar group of 10--15 x 7--10 cells; laminal cells (25--)40--70(--110) x 6--10 \um, leaves from the same shoot highly variable and ranging from 3--5:1 to 11--7:1. Branch leaves smaller, asymmetric at base and with margin recurved below broadest part of leaf on both sides, gradually acuminate, decurrent; costa strong, ending usually without an abaxial spine, margin slightly serrulate. Sexual condition autoicous. Seta reddish orange, 15--20 mm, rough but often rather indistinctly so. Capsule reddish orange, usually rather shortly ovoid, rarely ovoid-elongate, strongly inclined to horizontal or pendent, usually not curved or, when longer, slightly curved dorsally, ca. 1.2--1.4(--1.7) mm. Spores 13--16 \um.


Duff, decaying wood, humus, mineral soil, thin soil layer above rocks; 40--400 m in Alaska, 2000--3000 m in Rocky Mts., to 3630 m in New Mexico; B.C., Yukon; Alaska, Ariz., Colo., Idaho, Mont., N.Mex., Utah, Wash., Wyo.; Asia (Caucasus, Chukotka).


Sciuro-hypnum oedipodium has been usually identified as Brachythecium starkei by North American authors; S. Piippo (1983) demonstrated important differences, but included Brachythecium curtum in its synonymy causing additional problems as discussed by M. S. Ignatov and I. A. Milyutina (2007a). Sciuro-hypnum oedipodium is extremely variable in size of plants, for instance one of its synonyms, Brachythecium holzingeri, was originally described as a variety of Brachytheciastrum collinum, one of the smallest species of Brachythecium in the broad sense, while later it was synonymized with Sciuro-hypnum curtum, one of largest species. Most collections of S. oedipodium are of rather robust forms, but also exhibit plant size variation as well. Leaves from robust shoots usually have linear cells, whereas slender shoots from the same collection may have cells as short as those of S. reflexum or Brachytheciastrum collinum. However, the plant has a characteristic appearance, making it possible to recognize by often pale-brownish color (relatively pale leaves and brown stem cortex), leaves relatively densely arranged and plainly reflexed from appressed base, curved branches (similar to those of S. reflexum, but considerably larger), and often short capsules (also as in S. reflexum). Branch foliage is typically subjulaceous, more rarely homomallous to slightly falcate-secund. Sporophytes are frequent.


8. Sciuro-hypnum starkei (Bridel) Ignatov & Huttunen, Arctoa 11: 270. 2002 [2003]


Hypnum starkei [as starkii] Bridel, Muscol. Recent. 2(2): 107. 1801; Brachythecium starkei (Bridel) Bruch, Schimper & Gümbel.


Plants medium-sized, in loose tufts, green to yellow-green. Stems to 4 cm, prostrate to ascending and almost erect, flexuose, curved near apex, terete foliate, irregularly to fairly regularly pinnately branched; branches to 7 mm, often curved, terete to complanate-foliate. Stem leaves from erect-spreading to spreading at a wide angle, 0.8--1.6 x 0.4--0.8 mm, ovate-triangular, gradually tapered to apex or shortly acuminate, straight or acumen slightly falcate, smooth, margin serrulate, plane or recurved proximally; costa strong, in most leaves percurrent or vanishing within the narrow acumen, occasionally before mid leaf, ending in an abaxial spine, also abaxially toothed; juxtacostal basal cells shorter and slightly broader than laminal cells in ca. 2--3 rows, ca. 10 \um wide, with thick and porose walls; cells adjacent to decurrency much enlarged, to 25 x 17 \um, forming conspicuous pellucid group usually not reaching leaf margin; laminal cells 40--75 x 5--7 \um, elongate to linear, smooth or occasionally prorate in distal portion of the leaf. Branch leaves smaller, ovate to ovate-lanceolate, often symmetric, rarely asymmetric at base, acuminate, narrowly decurrent; costa in well-developed leaves percurrent, occasionally vanishing at mid leaf, ending usually without spine, occasionally in an abaxial spine and abaxially with several teeth, margins plane, more strongly serrulate to coarsely serrate; basal cells large across the base, distal laminal cells sometimes prorate. Sexual condition autoicous. Seta reddish, 12--16 mm, rough. Capsule reddish brown, oblong, horizontal to pendent, curved, especially when young (forming sometimes a 180--270° arch), ca. 2 mm. Spores 12--16 \um.


Soil, usually rich humus, wet places, swamps, forests; 100--1250 m; N.B., Nfld. and Labr. (Labr.), Ont., P.E.I., Que.; Maine, Vt., Wis.; n Europe, n Asia.


Sciuro-hypnum starkei is easy to confuse with Bryhnia novae-angliae and Kindbergia praelonga. From Kindbergia it differs in less regular pinnate branching, less well-differentiated stem and branch leaves, and acute juvenile branch leaves surrounding the young branch primordia; in Kindbergia, juvenile branch leaves are long-acuminate so groups of them around the branch primordia are quite conspicuous; they are usually quite numerous and some authors called them paraphyllia. The illustration of the gametophyte of Kindbergia praelonga in H. A. Crum and L. E. Anderson (1981; as Stokesiella praelonga) is Sciuro-hypnum starkei, especially because of the branching pattern and narrow leaf decurrencies. Differences from Bryhnia novae-angliae include consistently triangular stem leaves (in Bryhnia they are highly variable, with leaves in proximal part of branches shorter and acute to rounded) and percurrent costae (in Bryhnia they end at mid leaf). From both Bryhnia and Kindbergia, S. starkei differs in autoicous sexual condition. Bryhnia and Kindbergia neighbor Sciuro-hypnum in molecular phylogenetic trees (M. S. Ignatov and S. Huttunen 2002). Sporophytes are frequent.



9. Sciuro-hypnum latifolium (Kindberg) Ignatov & Huttunen, Arctoa 11: 270. 2002 [2003]


Brachythecium latifolium Kindberg, Forh. Vidensk.-Selsk. Kristiania 1888 (6): 8. 1888; B. nelsonii Grout; Sciuro-hypnum nelsonii (Grout) Ochyra & Żarnowiec


Plants medium-sized, occasionally large (tall), in loose tufts, light green to yellowish green. Stems to 3-6(--12) cm, prostrate to ascending, terete foliate, irregularly to rather regularly pinnate branching, branches to 8(--15) mm, straight to curved near their ends, terete-foliate. Stem leaves imbricate, 1.4--2.2 x 0.8--1.3, ovate-triangular, broadest at 1/7\x leaf length or below, gradually tapered towards apex or broadly rounded and then abruptly short and narrowly acuminate, sometimes with strongly serrate “shoulders” at the base of the acumen, rounded to base and decurrent with broad, pellucid cells, concave, not or slightly plicate, margin mostly plane, entire or minutely serrulate in acumen (especially at shoulders of the acumen); costa (0.2--)0.5--0.7\x leaf length, broad proximally but quickly narrowing at 0.1--0.2\x leaf length, very narrow along most of its length, ending without an abaxial spine, occasionally double from base to almost absent (in individual leaves of plants with otherwise 1-costate leaves); juxtacostal basal cells short or long rectangular in 2--3 rows, slightly broader than laminal cells, to 12 \um wide, thick-walled and porose, cells in leaf corners abruptly (or in very wet habitats somewhat more gradually) differentiated, often with characteristic delimiting pit at leaf border, 30--65 x 15-30(--35) \um, forming conspicuous pellucid alar group reaching 1/2--2/3 distance to costa; mid leaf cells elongate, (40--)70--140(--170) x 6--10 \um, smooth. Branch leaves similar, but smaller, or in narrow branches much narrower, almost entire, costa lacking terminal spine. Sexual condition dioicous. Seta reddish orange, 20--25 mm, rough. Capsule orange brown, inclined to horizontal or slightly pendent, ovate, curved dorsally, to 1.8 mm long, operculum high conic. Spores 13--16 \um.


Rocks, soil, rather wet and more or less open places, Arctic, alpine or northern boreal environments, among other mosses, wet tundra, rich fens; 0--3500 m; Greenland; Alta, B.C., N.W.T., Que., Yukon; Alaska, Calif., Colo., Mont., N.Mex., Utah, Wash., Wyo.; n Europe; n Asia.


Although relatively common in western Canada and in Alaska, Sciuro-hypnum latifolium is less common southwards, penetrating to New Mexico’s Sangre de Cristo Mts., at 3458 m. Usually S. latifolium is easy to recognize by medium-sized plants, 3--6 cm stems, pale color, and acute and strict distal leaves with more concave leaves in older parts of stem, which are more or less rounded distally and often relatively suddenly contracted to a short and narrow acumen that is usually somewhat reflexed. Its distal leaves are usually imbricate (appressed), but when growing among tall herbs in wet meadows and in minerotrophic fens (with Tomentypnum, Cinclidium, etc.) these leaves tend to be erectopatent; also, its stems are up to 12 cm. Other important diagnostic characters include subentire leaf margins, rather narrow laminal cells forming a dense areolation, and abruptly differentiated pellucid alar cells. The type of the synonym Brachythecium nelsonii was described in Wyoming, La Plata Mines. A. J. Grout (1928), as well as suggested in the original description, thought that S. nelsonii was related to B. rivulare and did not compare it with the Sciuro-hypnum glaciale-group, where S. latifolium belongs. The latter position was suggested by E. Nyholm (1965) and W. C. Steere (1978), and was recently confirmed by molecular phylogenetic analyses of S. Huttunen and M. S. Ignatov (2004) and I. Draper & L. Hedenäs (in press). Sporophytes are infrequent.


10. Sciuro-hypnum ornellanum (Molendo) Ignatov & Huttunen, Arctoa 11: 270. 2002 [2003]


Hypnum ornellanum Molendo, Ber. Naturhist. Vereins Augsburg 18: 185. 1865; Brachythecium ornellanum (Molendo) Venturi & Bottini; Scleropodium ornellanum (Molendo) Lorentz.


Plants medium-sized, in loose tufts, green to light green. Stems to 8 cm, prostrate to ascending, terete-foliate, irregularly to rather regularly pinnate branching, branches to 10 mm, straight to curved. Stem leaves imbricate, 1.2--1.8 x 0.7--1.1 mm, broadly ovate to broadly oblong, broadest at 1/5--1/7\x leaf length, broadly acute and often shortly apiculate, rounded to base and broadly but short-decurrent, strongly concave, not or slightly plicate, margin plane or recurved below, serrulate to subentire; costa to 0.2--0.7\x leaf length, broad proximally, rapidly narrowing distally, ending without an abaxial spine; basal cells indistinctly broader and shorter in a few rows, cells adjacent to decurrency subquadrate to short-rectangular, relatively thin-walled, 20--35 x 15--25 \um, forming a small pellucid group rather distinctly delimited from neighboring cells or sometimes only slightly differentiated; laminal cells 25--110 x 5--8 \um, elongate, smooth. Branch leaves similar, but smaller, or in narrow branches much narrower, almost entire, costa ending without abaxial spine; margins serrulate. Sexual condition autoicous. Seta reddish brown, 15--20 mm, rough. Capsule reddish to dark brown, inclined, shortly ovate-cylindric, slightly curved dorsally, to 2 mm long; operculum conic. Spores 16--20 \um.


Soil in poplar stands in hotspring areas; 400 m; Alaska; Europe; Asia (Kazakhstan, Kyrgyzstan, Russia).


Sciuro-hypnum ornellanum was recently discovered in Alaska by O. M. Afonina and A. Breen (2008) in two localities: Sagavanirktok Quad, Arctic National Wildlife Refuge, and Seward Peninsula, Pilgrim Hot Springs. Habitats were similar in both places: poplar stands close to hot springs. This species was expected in Alaska, as it occurs in nearby Chukotka, and it has a scattered but wide distribution throughout Siberia. Commonly, it grows there in tall-herb vegetation or in dwarf Betula and Salix communities with rich composition of herbs, that is, in places with relatively high snow accumulation in winter. The species is peculiar in the genus in its tumid foliage, and long was classified in the genus Scleropodium. However, it is distinct from the latter in the soft texture of plants (but rather rigid in Scleropodium), rather regular pinnate branching (irregular in Scleropodium), autoicous sexual condition, and the occurrence in Arctic and north boreal environments (as opposed to Mediterranean climates).


11. Sciuro-hypnum curtum (Lindberg) Ignatov, Arctoa 16: 50. 2007


Hypnum curtum Lindberg, Musci Scandinavici, 35. 1879; Brachythecium curtum (Lindberg) Limpricht


Plants medium-sized to robust, in loose tufts, often forming extensive cover; green, more rarely yellowish or brownish-green. Stems to 10 cm, ascending or more commonly arching, flexuose, terete to subcomplanate-foliate; branches to 10 mm, often curved, terete to complanately foliate. Stem leaves patent, loosely arranged, 1.4--2.4 x 0.9--1.5 mm, ovate or ovate-triangular (broadest at 1/7--1/10\x leaf length), gradually acuminate, slightly rounded to base, with decurrency proximally broad, then getting very narrow, slightly concave, not plicate, margins plane, serrulate; costa weak, reaching 0.3--0.75\x leaf length, ending without spine or with a small abaxial spine; basal cells broader and shorter in ca. 3 rows, cells in broad part of decurrency and the neighboring cells of leaf corner larger than juxtacostal basal cells, relatively thin-walled, 15--40 x 12--18 \um, forming extensive alar group delimited usually quite abruptly or occasionally rather gradually; mid leaf cells linear, smooth, 60--150 x 7--12 \um, Branch leaves smaller, ovate, often asymmetric at base and with margin recurved at base on one side, acute, narrowly decurrent; costa ending in some leaves in prominent spine and dorsally with several teeth, but in some leaves weak, vanishing and without a spine, margin more strongly serrulate to coarsely serrate distally; basal cells large across the base, laminal cells smooth. Sexual condition autoicous. Seta reddish, 17--32 mm, rough. Capsule reddish brown, oblong, horizontal to pendent, curved, especially when young (sometimes forming a 180--270° arch), ca. 2 mm. Spores 13--17 \um.


Forest floor, coniferous forests, soil rich in humus, logs, occasionally mineral soil and tree bases; mostly forests but also under tall herb vegetation; 0--900 m; Man., N.B., Nfld. and Labr. (Nfld.), N.S., Ont., P.E.I., Que.; Colo., Conn., Maine, Maryland, Mich. Mont., N.H., N.J., N.Y., Pa., Vt; W.Va; n Eurasia; Atlantic Islands.


In the west, Sciuro-hypnum curtum is known only from two collections: North American Mosses 259, Montana, Columbia Falls, R. S. Williams,1896 (NY), and Manitoba, south of Harashville, Mueller-Dombois 068--13 (MO). There was considerable confusion in naming this species. Most of collections in American herbaria are deposited under the name Brachythecium starkei. S. Piippo (1983) suggested this species this material was Brachythecium oedipodium, but M. S. Ignatov and I. A. Milyutina (2007a) found that the western North American S. oedipodium is different from S. curtum, being widespread Eurasian species that is more or less common in eastern North America but with few localities in the West. Thus the species name used by H. A. Crum and L. E. Anderson (1981) is resurrected here.


Sciuro-hypnum curtum is a variable in appearance, becoming very slender and loosely foliate in deep shade. It can usually be recognized by: (1) non-plicate, ovate to ovate-triangular leaves; (2) relatively short costa, often ending at 0.4--0.6\x leaf length; (3) pellucid group of cells adjacent to decurrency or sometimes extending to most of leaf base; (4) frequent presence of sporophytes; (5) coarse serration of leaf margin; (6) cells often longer than 100 \um in stem leaves, and (7) strongly curved capsules. Brachythecium rutabulum is a superficially similar species, and when optimally developed, is a densely foliate plant, forming rather dense tufts that never occur in S. curtum. Brachythecium rutabulum from deeply shaded habitats, however, may have loose tufts, nearly plane leaves, and strongly resemble S. curtum, and some collections are difficult to interpret. The leaf shape is probably the best character separating these species: the leaf of S. curtum from its broadest point is tapered at 35--45°, while for B. rutabulum at 30--35°, resulting in more acuminate leaves of the former. The patterns of decurrencies are also distinct: S. curtum has long and narrowly decurrent leaves, while in B. rutabulum decurrencies are triangular, and broad and rather short.


12. Sciuro-hypnum hylotapetum (N. Higinbotham & B. Higinbotham) Ignatov & Huttunen, Arctoa 11: 270. 2002 [2003]


Brachythecium hylotapetum N. L. Higinbotham & B. L. Higinbotham, Bryologist 61: 339. 1958


Plants robust, in loose tufts, forming extensive covers; whitish green to pale yellowish green, strongly glossy. Stems to 10 cm, prostrate, ascending to almost erect in dense growth, terete to complanate foliate, irregularly pinnate; branches to 16 mm, slightly curved or flexuose, indistinctly to often distinctly complanate-foliate. Stem leaves patent, loosely arranged, 2.2--3.7 x 1.3--2 mm, broadly ovate (broadest at about 1/7\x leaf length), shortly acuminate or apiculate, slightly rounded to base, short- and narrowly decurrent, not plicate, margins plane or recurved below widest point of leaf, serrulate to serrate in distalmost portion, but mostly slightly serrulate to subentire; costa broad near base but then evenly narrow, reaching 0.4--0.65\x leaf length, sometimes forked, ending without an abaxial spine; basal cells broader and shorter in ca. 2--4 rows, to 20 \um wide, cells adjacent -to decurrency larger, to 40--75 x 20--27 \um, forming a rather indistinctly delimited alar group; mid leaf cells linear, smooth, (80--)110--155(--185) x 7--13 \um, Branch leaves smaller, more gradually acuminate, more serrulate to serrate. Sexual condition dioicous, often without any gametangia. Seta chestnut to purple-red, 10--30 mm, rough. Capsule reddish brown, oblong, horizontal, curved, variable in length, 1.5--2.5 mm. Spores 12--20 \um.


Litter, duff, rotten wood, occasionally rocks and mineral soil in coniferous forests; 800--1500 m; Alta., B.C.; Idaho, Mont., Oreg., Wash.


The endemic Sciuro-hypnum hylotapetum has also been reported from Alaska (W. C. Steere 1978) and from California (D. H. Norris and J. R. Schevock 2004). The species is easy to identify by its robust stature, leaves longer than 3 mm, and the light green to whitish color. The usually apiculate leaves and the recurved leaf margins near the insertion are also diagnostic. Sporophytes are rare.




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