BFNA Title: Hypnum
Author: W. B. Schofield 
Date: April 6, 2006
Edit Level: R Brum+
Version: 2

Bryophyte Flora of North America, Provisional Publication
Missouri Botanical Garden

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Hypnaceae, Hypnum

 

Edit level R Brum+

 

XXX. HYPNUM Hedwig, Spec. Musc. Frond. 236.  1801, conserved name * [Greek hypnos, sleep, alluding to ancient use as filler for cushions]

W. B. Schofield

Breidleria Loeske; Drepanium C. Jens.; Pseudostereodon (Brotherus) Fleischer; Stereodon (Bridel) Mitten

 

Plants small to robust, 0.5-- -15 cm, 1--2-pinnate or irregularly branched; pseudoparaphyllia filamentous to foliose, toothed or blunt; axillary hairs 3--4-celled.  Stems with or without hyalodermis, with or without central strand.  Leaves of stem and branch similar but branch leaves tend to be smaller and narrower and with alar cells less well differentiated; broadly to narrowly ovate; margins sinuate to entire proximally, toothed to entire distally, sometimes recurved near base and usually plane distally; apex acuminate or acute; costa double or obscure, usually confined to proximal 1/4 of leaf; leaf cells usually smooth, usually elongate and somewhat vermicular, alar cells often differentiated as a distinct group of enlarged or diminished cells, often shorter than those of the rest of the leaf, indentation just above the alar region sometimes present;  axillary hairs with 1-4 (usually 1) short brownish basal cells and 2-5 (usually 3 and sometimes more) elongate hyaline distal cells; in most cases the walls thin and unornamented. Sexual condition autoicous, dioicous or phyllodioicous; inner perichaetial leaves erect, ovate to lanceolate or subulate, abruptly narrowed to a slender acumen, serrate or entire, plicate or not, outer leaves reflexed, costa single, double, or absent.  Seta smooth, yellowish to reddish. Capsule erect, inclined or horizontal, varying from long-cylindric to ovoid, usually curved, annulus 1--3 seriate to scarcely differentiated; operculum conic to rounded-mammillate; peristome double, exostome teeth subulate-acuminate, yellowish to brownish, outer surface with distinct zigzag line and lamellae, finely cross-striolate basally, hyaline and papillose distally, inner face trabeculate; endostomial segments about as high as exostomial teeth, pale and yellowish, carinate, weakly to strongly split between articulations, minutely papillose, cilia 1--3 or sometimes rudimentary.  Calyptra cucullate, naked.

 

Species ca. 50 (22 in the flora): widely distributed in all continents but Antarctica, but especially temperate areas.

 

SELECTED REFERENCES   Ando, H.  1972.  Studies on the Genus Hypnum.  I.  J. Sci. Hiroshima University,  Series B, Div. 2 (Botany) 14: 52--73.  Ando, H. 1973.  Studies on the Genus Hypnum II.  J. Sci. Hiroshima University,  Series B, Div. 2 (Botany) 14: 165--207.

 

The genus Hypnum remains a repository for a number of discordant elements, some considered to belong to other families. The genus once included a high proportion of the pleurocarpous mosses.  The generic concept accepted here contains some species probably not Hypnum, but it is a reasonably “natural” genus that can be recognized in the field, especially when examined with a hand-lens.  I have included Pseudostereodon, Drepanium, Breidleria and Stereodon within Hypnum, and remain unconvinced of arguments that they should be segregated.  Gametophytic features are supreme in separation of species although the presence of sporophytes provides additional features that strengthen the present species concept.

 

Size, branching patterns, leaf form and arrangement, areolation, especially alar cell differentiation, leaf margins, pseudoparaphyllium morphology, and stem anatomy are all features used here for taxonomic distinctions. With further analysis is possible that axillary hair morphology will prove to be a useful additional character to separate species. Unfortunately many of these features are altered by environmental extremes, especially in moisture and light.  In spite of this plasticity, most specimens can be named with reasonable confidence; there are, however, some specimens that cannot.  The problems in discriminating among the species have been considerably reduced through the elegant studies of H. Ando, but he treated only part of the genus in detail.  Fortuitously, however, he studied most of the species that occur in North America.

 

To use the key, a number of recommendations, if followed, are likely to yield more satisfactory determinations.  It must be noted again that some plants may be impossible to name satisfactorily.  Leafy plants of vegetative specimens may consist almost entirely of branches, with different but characteristic stem leaves unrepresented; this can happen when the plants form turf-like colonies or when the stem disintegrates, leaving only branches. Plants that grow in extreme environments, especially with respect to moisture, may be unusual; for instance, plants of deeply shaded or wet sites may be markedly attenuated.  Plants in highly illuminated and well-drained sites are also subject to morphological alteration that can “mimic” another taxon. Immature specimens can lack critical characters or are inconsistent in form. Intermixed material can contain several taxa, and it is necessary to tease out as complete a plant as possible for determination.

 

Thoroughly wet leafy shoots and remove branches before removing many leaves from the main stem and retaining the stripped shoot for determining form of the pseudoparaphyllia. Observations of leaf morphology should be based on many leaves. All the sections are on wet material in a drop of water on a microscope slide on a stage of a dissecting microscope. Remove leaves from the shoot by stripping them toward the stem base using fine-tipped forceps as aided by low magnification of a dissecting microscope.  It is important to get complete leaves, including the cells at the point of attachment to the stem.  In hyalodermous stems, the thin-walled cortical cells usually remain attached to the leaf base when the leaves are stripped from the stem; cross-sections can be made of the stem to confirm whether the stem is hyalodermous or not. Use sporangium-bearing specimens when possible to provide additional characters. In this key, the following features define differences in size of gametophores: small refers to stem leaves 1.2--1.5 mm and stems usually 1--2 cm and slender (related to the leaf size); medium refers to stem  leaves 1.5--3 mm and stems 2--4 cm; large or robust refers to stem leaves more than 3 mm and stem more than 4 cm. When length and width of leaves are given, length is cited first, and the width is that of the widest part of the leaf, usually the base

 

1. Leaves stripped from stem bearing thin-walled cortical cells; stems usually with hyalodermis.

2. Hyalodermis absent, but sometimes an interrupted epidermis of thin-walled cells, especially at leaf decurrencies .. 8. Hypnum fauriei (in part)

2. Hyalodermis present as a cortical layer.

3. Stem leaves gradually tapering to insertion, alar cells only slightly differentiated.

4. Plants somewhat flattened; with leaves not strongly secund, leaf apex broadly acute. . . ...................................................................................................... 17. Hypnum pratense

4. Plants never flattened; leaves falcate-secund, leaf apex narrowly acuminate.

5. Plants small (stem leaves 1.3--1.5 x 0.4--0.5 mm), usually erect and tuft-forming, laminal cells 40--60(--70) x 3--4 \um in lumen. . 10..Hypnum hamulosum

5. Plants medium-sized (stem leaves 1.5--2.8 x 0.4--0.6 mm) usually creeping and not tuft-forming, laminal cells 50--80(--90) x 3--4 \um; leaf acumen with sharp teeth   . . . 21. Hypnum subimponens

3. Stem leaves curved to insertion, sometimes auriculate, alar cells usually well differentiated.

6. Plants small (stem leaves 1--1.5 mm), stem leaves strongly curved to insertion, sometimes auriculate, alar cells differentiated in a small group at insertion………16. Hypnum plicatulum

6. Plants small to large, stem leaves weakly to strongly curved to base; alar cells forming a well-defined group, with the outermost cells thin-walled.

7. Plants small to medium-sized; stem leaves broadly ovate lanceolate, alar cells gradually enlarged downward, never decurrent . . . 11. Hypnum holmenii

7. Plants medium-sized to large; stem leaves ovate to oblong lanceolate; alar cells abruptly differentiated into well-defined group that is thin-walled, swollen and sometimes decurrent.

8. Alar cells weakly decurrent, usually not pronounced on dissection, 2--3 rectangular cells vertically and 3--4 cells horizontally, the outermost basal cells thin-walled and often collapsed inward, with a few triangular cells above the outer hyaline cell and cells beyond the thin-walled cells with thickened, often pigmented walls; stem red-brown to nearly black.. . . 7. Hypnum dieckii

8. Alar cells in a conspicuous decurrent group of thin walled, often swollen cells stripping off on dissection, without thicker-walled pigmented cells; stems yellow or reddish.

9. Plants medium sized to small, usually reclining, leaves with long-filiform serrulate acumen, stems yellow or green… . . 3. Hypnum callichroum

9. Plants large, often suberect, leaves with acute or broadly acute apex, older stems reddish . .  14. Hypnum lindbergii

1. Leaves stripped from stem without thin-walled cortical cells; stems lacking hyalodermis, but occasionally with scattered thin-walled cortical cells.

10. Leaves with margin strongly revolute from the base to upper portion . . . 20. Hypnum revolutum (in part)

10. Leaves with margin plane or sometimes recurved near base.

11. Stem leaves auriculate at insertion, auriculation sometimes only on one side.

12. Stem leaves with long-attenuate apex; cells below auricle enlarged and frequently reddish pigmented, much enlarged, alar cells few (5--6) in auriculation . . . 4. Hypnum circinale

12. Stem leaves gradually tapering to a point, not long-attenuate; cells below auriculate portion not conspicuously enlarged, or absent; alar cells numerous (more than 20) or reduced to less than 10.

13. Alar cells more than 20, not excavate; plants brownish, not glossy; plants closely pinnately branched . . . 18. Hypnum procerrimum

13. Alar cells less than 10, often excavate; plants yellowish to golden green, glossy; plants distantly pinnately branched . . . . . 6. Hypnum curvifolium

11. Stem leaves gradually curving to insertion, never auriculate.

14. Many stem leaves when stripped from stem bearing one or more elongate decurrent cells on margin.

15. Pseudoparaphyllia foliose or lanceolate, with incised margins… 12. Hypnum imponens (in part)

15. Pseudoparaphyllia foliorse or triangular to lanceolate, entire . . .  8. Hypnum fauriei (in part)

14. Stem leaves usually stripping from stem not bearing elongate decurrent cells.

16. Alar cells forming an extensive triangular area of 5 or more vertical rows of quadrate cells and few or no elongate cells at insertion.

17. Pseudoparaphyllia broadly foliose, blunt. . . 22. Hypnum vaucheri (in part)

17. Pseudoparaphyllia filamentous, lanceolate or lobed, sharply pointed.

18. Stem leaves strongly recurved near base and up margin; autoicous, sporophytes frequent . . . 19. Hypnum recurvatum

18. Stem leaves weakly recurved or plane near base; dioicous
or autoicous.

19. Plants slender, branch leaves (0.8--)1--1.4 x 0.2--0.4 mm.

20. Stem leaves falcate-secund, subentire to strongly toothed in long-attenuate apex . . . .............. 1. Hypnum andoi (in part)

20. Stem leaves weakly or not falcate, entire to weakly serrulate in apex . . .       5. Hypnum cupressiforme (in part)

19. Plants medium to large in size, branch leaves larger.

20. Plants robust, branch leaves 1.4--2.5 x 0.5--0.7 mm
 . . . 5. H. cupressiforme (in part)

20. Plants medium-sized, branch leaves 1.4--2 x 0.4--0.5 mm.

21. Plants pale green, strongly complanate, leaves loosely imbricate . . . 13. Hypnum jutlandicum (in part)

21. Plants greenish to golden or rusty green, never complanate, leaves strongly imbricate  . 5. Hypnum cupressiforme (in part)

16. Alar cells forming a small region of 1--3 rows of quadrate cells with 1-3 elongate cells at the insertion.

22. Pseudoparaphyllia filamentous to lanceolate.

23. Plants pale green, strongly complanate, leaves loosely imbricate . . . 13. Hypnum jutlandicum (in part)

23. Plants rusty to dark green to yellowish, never complanate, leaves closely imbricate.

24. Stem leaves falcate-secund, leaf apices strongly toothed, plants usually hanging downward on perpendicular substratum . . . 1. Hypnum andoi (in part)

24. Stem leaves falcate secund or straight, leaf apices entire or nearly so, plants usually creeping over horizontal substratum . . . 5. Hypnum cupressiforme (in part)

22. Pseudoparaphyllia foliose.

25.. Alar cells usually in dark brown group, often with an excavate group above the insertion; cells pitted throughout; plants usually dark chestnut brown and in seepage sites . . . 2. Hypnum bambergeri

25. Alar cells, if pigmented, usually reddish to yellowish, if excavate, the whole alar region involved; cells pitted only near base; plants pale rusty brown to golden green, usually in well-drained to dry sites.

26. Plants slender, alar cells unpigmented.

27. . Stem leaves toothed near apex, autoicous, often with sporophytes, epiphytic or xilicolous. . . 15. Hypnum pallescens

27. Stem leaves entire near apex, dioicous, sporophytes absent, terrestrial and calcicolous . . . 20. Hypnum revolutum (in part)

26. Plants medium-sized to robust; dioicous, alar cells pigmented or not.

28. Alar cells not pigmented or swollen at insertion. . . 22. Hypnum vaucheri (in part)

28. Alar cells with red-pigmented somewhat elongate swollen cells in 1--4 rows at insertion.

29. Pseudoparaphyllia bearing several sharp 1-seriate teeth … 12. Hypnum imponens (in part)

29 . Pseudoparaphyllia lanceolate, or if lobed, lacking additional teeth. . .  9. Hypnum fujiyamae

 

 

1. Hypnum andoi A. J. E. Smith, J. Bryol 11: 606.  1981 (1982)

 

Hypnum cupressiforme var. mammillatum Bridel; H. mammillatum (Bridel) Loeske, illegitimate name

 

Plants slender, pale green to yellowish green, 2--8 cm, reclining. Stems small, pale yellowish brown, creeping, closely affixed to substratum, epidermal cells not hyalodermous, central strand weakly developed; usually irregularly to regularly pinnately branched, branching arising in horizontal plane, pseudoparaphyllia subfilamentous to lanceolate, tipped by elongate cell.  Leaves weakly to strongly falcate-secund, ovate- or oblong-lanceolate, tapering gradually to base and tapering gradually to a short or more usually long acumen, 1--1.8 x 0.35--0.60 mm, margins usually sharply serrulate, often recurved near base, costa double, short or indistinct; median cells (40)50--60(--70) x 4--5 \um, basal cells shorter and wider, usually yellow or yellowish brown, alar region weakly excavate, often brown, of subquadrate cells (5--)7--10(--13) along margin, the marginal ones enlarged and hyaline, the inner brownish.  Sexual condition dioicous;  inner perichaetial leaves erect, oblong-lanceolate, suddenly narrowed to a long, serrulate acumen,  costa obscure.  Seta yellowish to reddish brown 0.08--1.7(--2) cm. Capsule yellowish to reddish brown, erect to inclined, oblong-cylindric 1.5--1.8(--2) mm; operculum conic (rounded-mammillate); annulus 2--3 seriate; cilia of endostome single or imperfectly double, very fragile.

 

Sporophytes produced in late autumn (September), capsules often maturing in spring (Mar.--Apr.), infrequent.  Perpendicular surfaces of tree trunks and rock cliffs; 0--2000 m; Nfld, N.S.; Maine; Europe.

 

Hypnum andoi is a temperate species of amphi-Atlantic distribution. This species resembles Hypnum cupressiforme var filiforme, but the leaves of H. andoi are long attenuate, and the row of basal hyaline cells in the alar region is decidedly different, reminiscent of Sematophyllum; the shorter, stouter capsule, and mammillate operculum are also valuable characters but sporophytes are extremely rare in North America, and have a conic operculum rather than a mammillate one, as in Europe.

 

2. Hypnum bambergeri Schimper, Syn. Musc. Europ. (ed.2) 698. 1860

 

Stereodon bambergeri (Schimper) Lindberg

 

Plants robust, 2--8(--10) cm, ascending to prostrate, reddish to yellowish brown, shiny, usually little and irregularly branched, but occasionally pinnately branched, with branches of variable length 0.2--0.6 cm, leafy stems 0.1--0.2 cm broad. Stems dark brown to reddish brown, with weak central strand; pseudoparaphylla wide, foliose.  Leaves of stem leaves falcate to circinate-secund, oblong-ovate to oblong-lanceolate, narrowed to a slender acumen, margins plane and sinuate to weakly serrate, 1.5--2 x 0.4--0.6 mm, curving gradually to alar cells, or forming a weak auricle just above the alar cells; costa single or double, and unequal, short to long, unequal; median cells 30--60 x 35--6 \um, somewhat to markedly pitted, cells of leaf base shorter and more strongly pitted, pigmented yellow to orange; alar cells in a well-defined, weakly to markedly excavate brownish group 3--7 cells high along margin and extending to 3--6 cells wide, quadrate to short-rectangular.  Sexual condition dioicous; inner perichaetial leaves erect, ovate to oblong-lanceolate, abruptly narrowed to a slender entire acumen, laciniate at shoulders, plicate.  Seta reddish brown, 1.3--2 cm.  Capsule yellowish brown, inclined to horizontal, 1.3--1.5 mm, excluding the conic operculum, cilia of endostome 2--3

 

Sporophytes infrequent, capsules mature summer (July, August). Often in seepage habitats, also in dry tundra, open conifer forest, mainly calcicolous; 0--2500 m; Greenland; Alta., B.C., Man., Nfld., N.W.T., Nunavut, Ont., Que., Yukon; Alaska, Mont.; Europe; Asia. 

 

Hypnum bambergeri is widely distributed in the Arctic and extends southward, especially in alpine sites. This species superficially resembles Limprichtia, from which it is readily separated by the single rather than double costa found in the latter genus, and also by the well-defined alar cells of H. bambergeri, absent in Limprichtia. The leaf cells pitted throughout separate this species from all others in Hypnum.  The usually calcareous terrestrial seepage habitat is also a useful trait.

 

3. Hypnum callichroum  Bridel, Bryol. Univ. 2: 631. 1827

 

Hypnum alaskae Kindberg; Stereodon callichrous (Bridel) Braithwaite

.

Plants medium-sized, 2--6 cm, branches 0.2--1 cm, regularly to irregularly pinnate, pale green to yellow-green, shiny, procumbent to ascending, firmly or loosely attached to substratum.  Stems yellowish to green, hyalodermous, with central strand, pseudoparaphyllia lanceolate. Leaves of stem falcate to circinate secund ovate to ovate-lanceolate gradually narrowing to a slender acumen, 1.5--2 x 0.75--0.8 mm, somewhat curved distal to alar region, margins plane, often sharply toothed in acumen that tapers to a 1-seriate apex, costa short and double or obscure, median cells linear, 50--60 x 8 \um, basal cells shorter, broader and porose, yellowish to unpigmented; alar cells forming a well defined region of thin-walled, often somewhat inflated cells 1--3 cells high and bounded by quadrate to triangular cells above.  Sexual condition dioicous;  inner perichaetial leaves erect, oblong-lanceolate and finely pointed, plicate, toothed near apex, costa obscure.  Seta 2--3.5 cm, red-brown, capsules red-brown, inclined, somewhat curved, 1.5--2 mm excluding conic operculum, annulus 1--2  seriate.

 

Sporophytes produced summer, capsules maturing June--July. Epiphytic or more usually terrestrial, forest, open terrain; 0--1500 m; Greenland; Alta., B.C.; Alaska, Wash.; Europe; Asia. 

 

In North America Hypnum callichroum is frequent only near the Pacific coast, where it is relatively easy to determine. The presence of a hyalodermis and the distinct alar region of thin walled cells that are strongly differentiated from the adjacent cells are reliable characters.  Material without sporophytes can, however, be troublesome.  Epiphytic specimens frequently have sporophytes, while the terrestrial ones generally lack them.  Although H. Ando has identified Arctic specimens as this species, I remain unconvinced.  This species is most likely to be confused with H. plicatulum and H. holmenii.

 

4. Hypnum circinale Hooker,  Musci Exot. 2: 21.  1820 

 

Hypnum squoitei J. K. A. Müller; Rhaphidostegium recurvans Kindberg; Stereodon circinalis (Hooker) Mitten

 

Plants light gray- to golden-green or dark green, 3--5(--10 or more) cm. Stems slender, irregularly to regularly pinnate (occasionally 2-pinnate) or irregularly branched, usually creeping and firmly affixed by rhizoids, reddish brown, lacking hyalodermis or central strand; pseudoparaphyllia filamentous to lanceolate, usually terminated by an elongate cell or 1-seriate tip 2--4 cells long. Leaves of stem falcate-secund to circinate, ovate- to triangular-lanceolate, often asymmetric at base with one side, somewhat to strongly auriculate, slightly decurrent, narrowing to a long acumination, 1.5--2.2 x 0.5--0.7 mm, margins serrulate, plane, rarely slightly recurved on one side, costae indistinct; branch leaves smaller, 1.1--1.5 x 0.3--0.4 mm, more strongly serrulate, median cells 60--80(--100) x 4--5 \um, with thin or thick porose walls, basal cells broader with porose walls, golden yellow, alar cells few, subquadrate to rounded-triangular, 2--5 in marginal row, proximal ones inflated, reddish brown, sometimes hyaline on margin. Sexual condition dioicous; antheridial plants similar to archegonial or phyllodioicous  with dwarf males epiphytic on archegonial plants;  perichaetial leaves erect, oblong-lanceolate, inner erect, the outer recurved, slender point serrulate, not plicate.  Seta smooth, reddish brown, 0.6--1.5(--2) cm. Capsule reddish brown, oblique to horizontal, ovoid to ovoid-oblong, 0.8--1.5 x 0.5--0.7 mm, operculum conic-apiculate, annulus 1--2 seriate; endostomial cilia 1--2.

 

Sporophytes produced autumn--winter (Sept.--Dec.), capsules usually mature Jan.--Feb.  Lowland to subalpine coniferous forests, commonly epiphytic on tree trunks, also on decaying logs and rock; 0--1500 m.; endemic to western North America; Alta., B.C.; se Alaska, Calif., Idaho, Mont., Oreg., Wash.

 

The often asymmetric stem leaves bearing a long-attenuate serrulate point, with one side auriculate with usually colored alar cells, the small sporangia that mature in early spring make Hypnum circinale an easy species to recognize.  Its closest affinities are with the east Asian H. tristoviride (Brotherus) Paris, which it strongly resembles in vegetative characters.  In eastern North America H. andoi resembles some forms of H. circinale in size and appearance, but the leaf bases, especially the nature of the alar cells as well as auriculation in H. circinale (absent in H. andoi) are reliable distinguishing features. On humid logs the plants tend to be larger than those on tree trunks and rock.

 

5. Hypnum cupressiforme Hedwig, Spec. Musc. Frond. 291.  1901

 

Hypnum pseudo-fastigiatum J. K. A. Müller; Stereodon cupressiformis (Hedwig) Mitten

 

Plants rusty green, golden green, yellow-green to pale green, medium sized to small, 2--10 cm, occasionally longer, prostrate to suberect. Stems pale to yellowish green, brown with age, epidermal cells not hyalodermous, central strand poorly developed, irregularly pinnate to nearly unbranched, shoots, attached shoots often regularly pinnate; pseudoparaphyllia filamentous, 1--3-seriate at base, but ending in elongated pointed 1-seriate tip.  Leaves weakly to decidedly falcate-secund, ovate to oblong-lanceolate, generally gradually curved to insertion and tapered to a slender acumen, 1.5--2 x 0.5--0.8 mm, margins serrulate (sometimes weakly) in distal half, occasionally nearly entire, recurved to plane proximally; costa double and short to obscure; median cells (50--)60--80 x 3--4(5) \um; basal cells shorter and wider; alar regions weakly or not excavate, made up of a well-defined triangular to quadrate area of many subquadrate cells or reduced to very few quadrate cells (sometimes pigmented), the more basal cells larger, sometimes hyaline, yellowish or brownish.  Sexual condition dioicous; inner perichaetial leaves erect, oblong-lanceolate, serrulate distally, not plicate; margins plane; costa obscure.  Seta reddish brown, 1--2.5(--3) cm. Capsule reddish brown, slightly inclined, cylindric and slightly curved, 1.8--2.5(--2.8) mm, excluding conic to rostrate operculum,  annulus 1--3-seriate; cilia of endostome usually 1--2(--3).

 

Varieties 9 in the world (4 in the flora):  Cosmopolitan; absent in Antarctica.

 

Hypnum cupressiforme is an extremely polymorphic species, reflected in the more than 60 varieties that have been described. It has a wide ecological amplitude as well as a cosmopolitan world distribution and is found in all climatic regions. Taxonomic features reliable in most other species of Hypnum are plastic in H. cupressiforme. Within a single clone it is possible to sort out several named varieties. Hypnum cupressiforme var. lacunosum Bridel was noted by H. Ando (1989) to be weakly differentiated in North America, and tentatively cited specimens from Nova Scotia, Newfoundland, and South Dakota. Ando noted that the var. lacunosum typically is robust, thick-complanate to julaceous, with leaves almost straight to weakly falcate and abruptly narrowed to a short acumen, but the North American material is not robust and is therefore problematic.

 

1. Plants small, branch leaves 1--1.4 x 0.2-0.4 mm or slightly less.

2. Leaves straight to slightly falcate, entire to weakly toothed distally.

2. Leaves falcate-secund, subentire to distinctly toothed distally . . 5a. Hypnum cupressiforme var. cupressiforme (in part)

3. Plants subjulaceous to filiform, prostrate, leaves oblong-lanceolate, gradually narrowed to acumen; cells 60--80 x 3--4 \um (or slightly greater)……………………. 5b. Hypnum cupressiforme var. filiforme

3. Plants julaceous, usually in compact tufts; leaves ovate or widely oblong-lanceolate, abruptly narrowed to short acumen; median cells shorter and broader, 40--50 x 5--6 \um …. 5c. Hypnum cupressiforme var. julaceum

1. Plants medium-sized to robust, branch-leaves 1.5--2 x 0.4-0.6 mm or slightly greater.

4. Plants robust, branch leaves 1.4--2 x 0.4--0.7 \um or greater, branches not or rarely flagellate at tips . . . . [Hypnum cupressiforme var. lacunosum]

4. Plants medium-sized, branch-leaves 1.5--2.5 x 0.5--0.8 mm or greater.

5. Plants weakly complanate, leaves falcate-secund; alar cells not excavate or colored…5a. Hypnum cupressiforme var. cupressiforme (in part)

5. Plants subjulaceous to complanate; leaves straight to weakly falcate; alar cells often excavate and colored . . . . 5d. Hypnum cupressiforme var. subjulaceum

 

 

5a. Hypnum cupressiforme Hedwig var. cupressiforme

 

Plants varying from slender to medium-sized and in color from pale green, dark green to golden-brown; length various; branching pinnate to irregular, reclining to suberect. Leaves usually falcate, sometimes strongly; alar cells numerous to few, usually not excavate.

 

Producing sporophytes late summer--fall, capsules often mature spring. Terrestrial, epiphytic, epilithic; 0--4000 m; Greenland; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S., Nunavut, Ont., P.E.I., Que., Sask., Yukon; Alaska, Ark., Colo., Conn., Del., Ill., Iowa, Maine, Md., Mass., Mich., Mont., N.Y., N.C., Pa., S.Dak., Vt., Tex., Wash., Wis.; Mexico; South America; Eurasia; Africa; Atlantic Islands; Pacific Islands (New Zealand); Australia.

 

Hypnum cupressiforme var. cupressiforme is used as a catch-all to accommodate specimens that cannot be placed in another of the 9 varieties recognized by H. Ando including those accepted here.

 

5b. Hypnum cupressiforme var.  filiforme Bridel, Musc. Rec 2: 138.  1801

 

Plants slender, pale green to dull green, occasionally yellowish green, 2--6 cm, irregularly to somewhat pinnately branched, some branches frequently filiform.  Leaves subjulaceous, straight to somewhat falcate, gradually narrowed to slender acumen, nearly entire, alar cells subquadrate, usually in a well-defined group. Sporophytes unknown in North America, rare in the entire range.

 

Mainly confined to perpendicular surfaces of cliffs and tree-trunks; 0--2500 m; N.B., N.S., P.E.I.; Ark., Conn., Maine, Mass., Mich., N.H., N.J., N.Y., N.C., Okla., Pa., Tenn., Tex., Va; South America (Chile); Europe; Asia; Africa; Pacific Islands (New Zealand); Australia.

 

When well developed, Hypnum cupressiforme var. filiforme is distinctive, with filiform julaceous stems and straight leaves.  There are variants with somewhat falcate-secund leaves that can be confused with H. andoi.  The latter species rather has long-attenuate leaf apices, is not julaceous, although filiform, and the leaves are not strongly imbricate as in var. filiforme.  The many specimens that closely resemble var. filiforme strongly suggest that it may be an environmental form induced by the habitat that holds moisture rather briefly during the growing season.

 

5c. Hypnum cupressiforme var. julaceum Bridel, Musc. Recent. Suppl. 2: 216.  1812.

 

Plants tufted, medium sized, prostate to erect, to 5 cm, densely to loosely pinnately branched, sometimes asymmetric, branches 0.2--1.5 cm, julaceous. Leaves straight to weakly falcate, ovate or widely oblong, concave, acumen abruptly narrowed to short-acuminate, subentire. Seta 1--1.5 cm. Capsules ca. 1 mm.

 

Confined to horizontal, rather than vertical surfaces, strongly illuminated sites, especially in mountains and at higher latitudes; 100--2500 m.; N.W.T., Yukon; Alaska, Colo.;  Europe; Indian Ocean Islands (Kerguelen).

 

5d. Hypnum cupressiforme var. subjulacuum Molendo, Ber. Naturhist. Ver. Augsburg 18: 183.  1865

 

Plants creeping, medium-sized, yellowish green to brown, lustrous, usually prostrate, 5--8 cm or more, regularly to irregularly pinnate, to 2-pinnate, occasionally plumose on one side, branches 0.2--1(--1.5) cm, subjulaceous, sharply pointed.  Leaves of stem oblong-lanceolate, straight to weakly falcate, sometimes homomallous, gradually narrowed to long and slender acumen, somewhat concave, margins subentire to weakly toothed, weakly recurved near base or plane throughout; alar cells subquadrate, often brownish, often in excavate group. Sporophytes unknown in area of flora.

 

Terrestrial, cliff shelves, horizontal rock surfaces, in both exposed and sheltered sites, predominantly calcareous substrata; 0--4000 m; B.C., Yukon; Alaska, Colo., N.Mex., N.Dak.; Europe (mainly high elevations); Asia; Pacific Islands (New Zealand).

 

This variety is frequent in the Alaskan Peninsula but uncommon (or unrecorded) elsewhere in North America.  I have seen no sporophytes in North American material.  The acutely attached branches, closely imbricate, straight leaves with sharp apices and frequently excavate colored alar cells make this a distinctive variety.

 

6. Hypnum curvifolium Hedwig, Spec. Musc. Frond. 285.  1801

 

Stereodon curvifolius (Hedwig) Mitten

 

Plants medium-sized to robust, procumbent to suberect, light green to yellow-green, generally regularly pinnately branched, 4--10 cm; branches to 1.5 cm, leafy stems 0.5--3 mm wide. Stems orange brown to reddish, hyalodermis absent, central strand weakly differentiated; pseudoparaphyllia foliose. Leaves of stem ovate, falcate-secund, 1.5--2.5 x 0.7--0.8 mm, narrowing to a relatively broad acumen, curving to the insertion, slightly decurrent, margins plane, sinuose to entire near base, gradually weakly toothed near apex; costa short and double; median leaf cells 70--80 x 4--5 \um, stouter at apex and at insertion where broader and pigmented, median cells sometimes projecting abaxially at distal end of cell, especially near apex; alar cells few, hyaline and enlarged, in 1--3 rows across base, delimited by smaller ovoid to triangular cells distally. Sexual condition dioicous; inner perichaetial leaves erect, lanceolate to subulate, tapering gradually to apex, somewhat plicate.  Seta 2--4.5 cm, orange-yellow to brownish when mature. Capsule reddish brown, obovoid-cylindric, 2.5--3 mm excluding conic operculum, strongly curved, plicate when dry, annulus broad, 2-seriate, cilia of endostome 2--3, nodulose.

 

Sporophytes produced in summer; capsules mature July--Aug. Terrestrial or most commonly on decaying logs in woodland, also rock, occasionally in peatland; 0--2000 m; N.B., Nfld., N.S., Ont., P.E.I., Que.; Ala., Ark., Conn., Del., D.C., Ga., Ill., Ind., Iowa, Kans., Ky., La., Maine, Md., Mass., Mich., Minn., Miss., Mo., Nebr., N.H., N.J., N.Y., N.C., Ohio, Okla., Pa., R.I., S.C., Tenn., Tex., Vt., Va., W.Va., Wis.

 

Hypnum curvifolium is an eastern North American endemic. It might be confused with H. lindbergii from which it differs in the more extensive and often decurrent alar region of H. lindbergii and the more plumose branching in H. curvifolium. In Hypnum lindbergii, the leaves are never as circinate as those of Hypnum curvifolium.  The presence of an hyalodermis in H. lindbergii and its absence in H. curvifolium further separates these species. From H. imponens, usually smaller, the characteristic toothed pseudoparaphyllia of that species separate it.

 

7. Hypnum dieckii  Renauld & Cardot, Bot. Centralbl. 44: 423.  1890

 

Stereodon dieckii (Renauld & Cardot) Brotherus

 

Plants medium-sized, 4--8 cm, generally regularly pinnate, dark green to golden green or nearly black, procumbent to suberect, often firmly attached by rhizoids, but when suberect generally without rhizoids; branches 0.2--1.5 cm, leafy stems 0.05--0.15 cm wide Stems red-brown to nearly black, hyalodermous, central strand poorly differentiated; pseudoparaphylla foliose, broad. Leaves of stem falcate, leaves curved downward towards substratum, ovate-lanceolate, tapering to a narrow acumen, 1--1.5 x 0.4--0.5 mm, curving slightly to insertion, margins plane, entire to sinuate in basal half, but often sharply serrate toward apex, costa usually indistinct; median cells 40--60 x 3--4 \um, basal cells often pigmented yellowish to brownish, especially adjacent to hyaline alar cells, porose, rectangular, shorter and wider than median cells; alar cells in a well-defined excavate group of thin walled, mainly rectangular cells, area 2--3 cells high and 3--4 cells deep, the outer ones thin-walled and somewhat collapsed inward, with a few triangular cells distally, often bulging 40--65 x 20--30 \um.  Sexual condition dioicous; inner perichaetial leaves erect, lanceolate and finely pointed, plicate, toothed, costa obscure. Seta 2--4.5 cm, red-brown when mature.  Capsule red-brown,usually nodding when mature, 3--4.5 mm excluding conic operculum, annulus 1--2-seriate,  cilia of endostome rudimentary.

 

Sporophytes produced summer; capsules mature June-July. Terrestrial, rocks, logs, near water courses, seepage areas, open to somewhat shaded areas, but usually where persistent moisture is available; 0--1500 m; B.C.; Alaska, Calif., Oreg., Wash; Asia (Japan south to Kyushu).

 

Hypnum dieckii is distributed around the north Pacific, and can be frequent on logs or outcrops near streams. This is a distinctive species, especially when sporophytes are present, as it is the only North American species that has nodding capsules.  The dark stems, and pinnate branching associated with the excavate region of thin-walled alar cells set off by inner thick-walled and pigmented basal cells, are usually enough to separate it.  It can be distinguished from Hypnum lindbergii by the decurrent thin-walled alar cells and the longer and weakly toothed leaves of that species.

 

8. Hypnum fauriei  Cardot, Beih. Bot. Centralbl. 17: 41.  1904

Hypnum fertile of American authors, not Sendt.

 

Plants creeping, medium-sized, 4--8 cm, ca. 0.13 cm broad including leaves, yellowish brown to brownish green, somewhat glossy, often densely branched, regularly to irregularly pinnate, often attached to substratum by numerous rhizoids; branches up 1 cm, ca. 0.08 cm wide (with leaves).  Stems lacking hyalodermis, reddish to yellowish; pseudoparaphyllia foliose, triangular to lanceolate.  Leaves of stem falcate to circinate, from broadly ovate base, tapering to a slender acumen and narrowing to insertion, sometimes weakly cordate, 1.4(--2.2) x 0.4(--0.75) mm, yellowish brown at base, margin crenate to entire or toothed in acumen, proximal margin excavate in alar portions where the cells are often colored, hyaline and few (1--3), rectangular to quadrate and often bulging with 2 or 3 subquadrate to rectangular cells distally, sometimes with rectangular decurrent cells at insertion; median laminal cells linear to slightly vermicular, 50--70(--80) x 3--5 \um, basal cells shorter and thicker with thicker porose walls. Sexual condition autoicous.  Seta 3--4 cm, reddish brown or yellowish brown.  Capsule inclined to horizontal, cylindric, 2--3 x 0.9--1 mm, curved, brown when mature, operculum conic-apiculate, annulus 3-seriate, cilia of endostome 2--3, endostome segments with large perforations.

 

Capsules mature summer (July).  Tree bases, stumps, rotten logs, occasionally on humus and rock, mixed forest; 0--2000 m, lower elevations in the northern part of the range but at higher elevations in the mountains southwards; N.B., N.S., Ont., Que.; Ga., Maine, Mich., Minn., N.H., N.Y., N.C., Pa., Tenn., Vt., Va., W.Va.; E Asia: Korea, Japan, Russia (Altai).

 

Hypnum fauriei has posed difficulties since its early report from North America as H. fertile, a species restricted to Europe.  It appears to be uncommon, but superficial examination could allow misidentification as H. imponens or even H. plicatulum.  The larger number of alar cells that are often delimited by colored cells nearby easily distinguish H. imponens from H. fauriei; the broad, foliose, much-toothed pseudoparaphyllia that are usually frequent in H. imponens differ markedly from the triangular to lanceolate pseudoparaphyllia occasionally found in H. fauriei. In addition, the erect rather than inclined capsules also immediately separate H. imponens.  Hypnum plicatulum has few alar cells, but the leaf bases are somewhat to strongly auriculate, the plants are yellow-green, and the hyalodermous stem cells are apparent, all features lacking in H. fauriei.

 

9. Hypnum fujiyamae (Brotherus) Paris, Ind. Bryol., suppl. 202.  1900

 

Stereodon fujiyamae Brotherus, Hedwigia 38: 232.  1899

 

Plants robust, prostrate to suberect, 3--15 cm, branches 2--5 cm, sometimes longer, leafy stems 0.2--0.25 cm broad; golden to rusty green, shiny, irregularly to distantly pinnately branched, stem apices markedly pointed with imbricate leaves. Stems yellowish brown, central strand weakly developed; pseudoparaphyllia lanceolate to ovate, foliose, lacking cilia. Leaves of stem usually falcate-secund, ovate-lanceolate to ovate, gradually acuminate 0.2--3 x 0.1--1 mm, plicate, acuminate, somewhat toothed, margins sometimes recurved in proximal half, rarely nearly to apex; costa double, faint to distinct, basal cells thicker walled and porose, sometimes brownish yellow, alar cells well defined, forming a group 3--4 cells deep and 5--8 cells wide at base, the inner ones usually colored, grading into the basal cells, outer cells inflated somewhat and thin-walled, hyaline to yellowish, grading to brownish, subquadrate to rectangular supra-alar cells, the leaf margin curved above them, sometimes slightly auriculate. Sexual condition dioicous or phyllodioicous. Sporophytes lacking in area of flora.

 

Usually tundra fen slopes over shallow peat in late-snow lying sites; mainly near 200 m; Alaska (Attu I.); Asia (Japan, Korea, mainly at higher elevation, except northern part of range).

 

Hypnum fujiyamae somewhat resembles H. lindbergii in the field but the golden to brownish color of the plants and the imbricate cuspidate apices of the shoots mark it as different. While H. lindbergii forms turf-like mats, H. fujiyamae has reclining shoots. Microscopically these species are clearly unrelated.

 

10. Hypnum hamulosum  Schimper in P. Bruch, W. P. Schimper & W. Gümbel, Bryol. Eur. 6: 96. pl. 590. (fasc. 57--61. Monogr. 20. plate 10: hamulosum).  1854

 

Stereodon hamulosus (Schimper) Lindberg

 

Plants small, yellowish, pinnate to irregularly branched, forming turfs of erect to suberect shoots or creeping, 2--9 cm, branches 0.4--0.8 cm, slender.  Stems yellowish, with hyalodermis and weak central strand; pseudoparaphyllia scarce, foliose. Leaves of stem strongly hamate and falcate-secund, ovate-lanceolate, slightly tapered to base, 1 x 1.5 mm, margins plane, mostly entire but weakly toothed toward apex; cells narrowly vermiculate, with blunt ends, 6--7 x 60--75 \um shorter and broader toward base; alar cells rarely differentiated except at margin and near insertion, with 2--3 slightly larger, thin-walled cells. Sexual condition phyllodioicous; perichaetial leaves erect, except the outermost reflexed, plicate, with attenuate toothed apex. Seta 1--2 cm, reddish. Capsule inclined to horizontal, long-cylindric, urn 1.5--1.8 mm, operculum conic, 0.5 mm; annulus 2--3-seriate cilia of endostome 1--2, smooth.

 

Capsules mature July--August, infrequent. Predominantly on calcareous rocks, in crevices, also reported in tundra, mountains in southern part of its range; elevation not determined; Alta., B.C., N.W.T., Nunavut, Yukon; Greenland; Alaska, Colo.(?); Europe; Asia.

 

Hypnum hamulosum resembles the related species H. callichroum, H. holmenii, and H. plicatulum, especially the last two, but differs in its strongly hamate stem leaves that generally do not taper to the base and usually lack differentiated alar cells.  Branch leaves are not diagnostic, and tundra forms can be impossible to name with confidence.  These often possess only branch leaves as the main stem is not present. Many reports of H. hamulosum from North America are based on such specimens.

 

11. Hypnum holmenii Ando, Hikobia 11. 365.  1994

 

Stereodon holmenii (Ando) Ignatov & Ignatova

 

Plants small, regularly to irregularly and densely pinnately branched, pale green to yellow-green, shiny, ascending to procumbent, 4--6 cm, branches to 1 cm, loosely affixed to substratum, turf or weft-forming.  Stems yellowish, hyalodermous, with weak central strand, pseudoparaphyllia foliose, lanceolate, irregularly dentate.  Leaves of stem falcate, secund broadly ovate-lanceolate, gradually narrowed to a slender acumen, curved to insertion (sometimes markedly), 1.4--1.6 x 0.5--0.6 mm, margins plane and serrulate distally, costa short and double; median cells linear (50--)60--80 x 3--4 \um, basal cells shorter and wider, yellowish or unpigmented; alar regions are distinct areas of subquadrate to rectangular cells, 9--20 \um wide, usually not decurrent, the most basal cells thinner walled and hyaline, often tearing away with the enlarged stem cortical cells; branch leaves similar.  Sexual condition dioicous or phyllodioicous; perichaetial leaves erect, oblong-lanceolate, with slender serrulate acumen, plicate, costa obscure.  Seta 1.5--2.2 cm, pale reddish brown. Capsule red-brown, inclined to horizontal, oblong-cylindric, curved, 1.5--1.8 mm, excluding conic operculum; annulus 1--2-seriate, cilia of endostome 2--3.

 

Sporophytes produced summer; capsules mature July--Aug. Mainly in moist heaths, but also shrub thickets and spruce forest, largely on calcareous substrata; 0--1500 m or more; Greenland; Alta., B.C., N.W.T., Nunavut, Yukon; Europe (Finland).

 

Hypnum holmenii occurs mainly at elevations above 1500 m. In size and general aspect this species often resembles H. plicatulum, but the leaves are generally not markedly auriculate, as in H. plicatulum. The enlarged alar cells are not differentiated in the latter species, while they usually are in H. holmenii.  From Hypnum callichroum, it differs in the abruptly differentiated group of enlarged alar cells of the former, these gradually differentiated in H. holmenii.  It is necessary to examine many leaves to achieve an accurate assessment. Hypnum hamulosum differs in its strongly hamate stem leaves and the less differentiated alar cells.  Because H. holmenii often resembles related species, its distribution has been inadequately documented.

 

12. Hypnum imponens  Hedwig, Spec. Musc. Frond. 290.  1801

 

Stereodon imponens (Hedwig) Mitten

 

Plants golden to yellow-green or brownish, medium-sized to large, creeping, 3--10 cm.  Stems reddish brown, central strand weak, hyalodermis not differentiated from the cortical, usually regularly pinnately branched, occasionally partly 2-pinnate, or irregularly branched; branches usually in a single horizontal plane, 0.3--1.2 cm; pseudoparaphyllia frequent, lanceolate or foliose, mostly with incised margins. Leaves of stem falcate-secund, triangular-ovate to oblong-lanceolate, gradually narrowed to a slender acumen, 1.8--2 x 0.6--0.8 mm, weakly to not plicate, margins serrulate in distal half of leaf or rarely nearly entire, plane or weakly recurved near base;  costa short and double or indistinct; median cells 50--70(--80) x 3--4(--5) \um, sometimes porose; basal cells broader and colored yellow-orange to orange-brown, especially in inner portion of alar region; alar portion not to weakly excavate, somewhat decurrent, of subquadrate cells, the basal ones often heavily pigmented orange-brown, the outer cells hyaline with thinner outermost marginal wall, 5--10 cells high on margin. Sexual condition dioicous; inner perichaetial leaves erect, oblong-lanceolate, with long, serrate acumen, often strongly revolute margined in proximal half, plicate, costa indistinct.  Seta red-brown, 1--3 cm. Capsule red-brown erect to slightly inclined and somewhat curved below mouth, cylindric, 1.5--3 mm, excluding the conic to rostellate operculum; annulus scarcely differentiated, cilia of endostome usually single, sometimes rudimentary or double.

 

Sporophytes produced, sometimes abundantly, in summer, capsules mature July--Sept.  Commonly on decaying logs, but also rock and soil; 0--2000 m; s Greenland; N.B., Nfld., N.S., Ont., P.E.I., Que.; Ala., Ark., Conn., Del., D.C., Fla., Ga., Ill., Ind., Iowa, Ky., Me., Md., Mass., Mich., Minn., Miss., Mo., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., S.C., Tenn., Tex., Vt., Va., W.Va., Wis.; Europe.

 

Hypnum imponens is an amphi-Atlantic species. The often colored, heterogeneous alar cells, usually reddish stem, long-toothed foliose, usually numerous, pseudoparaphyllia, and the nearly erect, cylindric capsules are characteristic.  The lanceolate or filamentus pseudoparaphyllia and generally homogeneous alar cells of H. cupressiforme and its near relatives are usually sufficient to separate them from this species.

 

13. Hypnum jutlandicum  Holmen & E. Warncke in K. Damsholt, K. A. Holmen & E. Warncke, Bot. Tidsskr. 65: 179.  1969

 

Hypnum cupressiforme var. ericetorum Bruch, Schimper & W. Gümbel

 

Plants medium-sized to slender, prostrate, ascending or erect, 4--10 cm, pale green; branches emerging in horizontal plane, 0.4--0.7 cm, occasionally longer.  Stems yellowish green to pale brown, central strand weakly developed, epidermal cells not differentiated; densely to sparsely pinnately branched; pseudoparaphyllia filamentous to lanceolate, occasionally forked, terminated by 1-seriate tip of several elongate cells.  Leaves loosely imbricate, straight to falcate-secund, ovate or oblong-lanceolate, gradually narrowed to short acumen, 1.7--2.2(--2.5) x 0.6--0.8(--0.9) mm; margins usually markedly serrulate distally, plane or recurved near base; costa short or indistinct, double; median cells (60--)70--90(--100) x ca. 3 \um; basal cells shorter and broader and thicker walled, often porose, light yellow or colorless; alar region usually strongly excavate, sometimes brown, distal cells subquadrate and 3--5(--7) along margin, the proximal cells somewhat enlarged and somewhat decurrent at extreme marginal cell. Sexual condition dioicous; inner perichaetial leaves erect, oblong-lanceolate, suddenly narrowed into a distinctly serrulate acumen, not plicate, costa indistinct.  Sporophyte unknown in North American material and rare in Europe. [Seta yellowish to reddish, 2.5--4 cm. Capsule reddish brown, inclined to horizontal, oblong-cylindric, slightly curved, 1.5--2  mm excluding rostrate operculum; annulus 2-seriate; cilia of endostome usually single, sometimes rudimentary.]

 

Capsules (in Europe) mature winter--spring.  Terrestrial; 0--500 m; Nfld., N.S.; Alaska (?); Europe; Africa (Azores).

 

Hypnum jutlandicum is largely an amphi-Atlantic species. The pale yellowish green, glossy, pinnate plants are very distinctive and might be confused with H. imponens, but H. jutlandicum has yellow rather than red-brown stems, and the leaves tend to be golden yellow rather than pale yellow; and the pseudoparaphyllia of H. imponens are more broadly foliose than the nearly filiform ones of H. jutlandicum.  Distinction from H. cupressiforme is less apparent, but the usually more complanate pale green plants of H. jutlandicum are usually sufficient to separate it.

 

14. Hypnum lindbergii  Mitten, J. Bot. 2: 123.  1864

 

Calliegonella lindbergii (Mitten) Hedënas; Hypnum arcuatum Lindberg, illegitimate homonym; H. patientiae Milde, illegitimate name, H. acuatum var. americanum Renauld & Cardot; Stereodon patientiae Lindberg; H. arcuatiforme Kindberg; H. renauldii Kindberg

 

Plants golden green to yellow-green to pale green, glossy, soft, large to small, 1--5 cm, varying from irregularly branched to few branched to somewhat pinnately branched, branches 0.2--2 cm.  Stems reddish brown to yellowish green, brown with age, epidermal cells conspicuously hyalodermous, central strand well developed, suberect to prostrate; rhizoids usually rare to absent; pseudoparaphllia foliose.  Leaves falcate-secund (sometimes weakly so), oblong-ovate, tapering gradually to a slender or broad acumen, 0.5--2 mm x 0.5--1 mm, decurrent, not or slightly rounded to insertion, margin entire to blunt serrate especially in acumen, plane; costa short and double; median cells linear 60--100 x 5--6 \um wide, basal cells yellowish, porose, wider and shorter; alar cells in a decurrent group of well-defined marginal group, usually swollen and thin walled, in 2--4 rows, delimited by 1--3 rows of shorter cells distally. Sexual condition dioicous; inner perichaectial leaves erect, oblong-lanceolate, deeply plicate, attenuate, margins serrulate at tip, costa obscure.  Seta reddish brown, 2.5--4 cm, capsule pale brown, inclined, cylindric, curved, 2--3  mm, excluding conic-convex operculum; furrowed when dry; annulus 2--3 seriate; cilia of endostome 2--4, as long as segments.

 

Producing sporophytes infrequently spring--summer; capsules maturing June--Aug. Terrestrial, commonly in open sites, wet soil, humus, logs, sand of lake and river margins, swamp forests; 0--3000 m; Greenland; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S., Nunavut, Ont., P.E.I., Que., Sask., Yukon; Ala., Alaska, Ariz., Ark., Calif., Colo., Conn., Ill., Maine., Md., Mass., Mich., Minn., Miss., Mo., Mont., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Okla., Pa., R.I. S.C., S.Dak., Tenn., Tex., Utah, Vt., Va., Wash., W.Va., Wis., Wyo.; Europe; Asia.

 

Hypnum lindbergii is largely a species of temperate climates, most frequent in boreal and warm temperate regions, less frequent in the arctic, occurring from sea level to alpine elevations. The hyalodermous cortical cells, leaves usually curved to insertion, usually well-defined alar regions of swollen thin-walled cells, and often wide acute apex of many stem leaves usually separate this species from similar taxa.  Hypnum pratense resembles it somewhat, but tends to be very glossy, the stem leaves often complanate, and thin-walled alar cells are lacking. With further study, H. lindbergii var. americanum (Renauld & Cardot) Whitehouse may prove to be worthy of recognition.

 

15. Hypnum pallescens  (Hedwig) Palisot de Beauvois, Prodr. 67.  1805

 

Leskea pallescens  Hedwig, Spec. Musc. Frond. 219.  1801; Hypnum reptile  Michaux; Hypnum pallescens var. protuberans (Bridel) Lesquereux & James; Stereodon pallescens (Hedwig) Mitten; H. depressulum J. K. A. Müller

 

Plants yellowish to golden green, dark green or dirty brown, regularly to irregularly pinnately branched, usually creeping and firmly affixed by rhizoids, 2--5 cm; branches emerging in plane parallel to substratum, slightly flattened to somewhat julaceous, 0.2--0.4(--6) cm.  Stems slender, yellowish to golden green, not hyalodermous, with central strand weakly developed; pseudoparaphyllia lanceolate, infrequent.  Leaves falcate-secund, rarely straight, ovate- to oblong-lanceolate, not or weakly decurrent, narrowed into a short acumination that varies from slender to relatively wide; margins serrate distally, serrulate to nearly entire proximally, usually broadly or narrowly recurved proximally but sometimes to the leaf length; costa faint to distinct, rarely single; median cells 30--50 x 4--5 \um, weakly papillose at ends; basal cells broader and often yellowish; alar cells subquadrate or transversely rectangular 8--15(--20) in marginal row, subopaque; stem leaves wider 0.6--1.1 x 0.4--0.6 mm, branch leaves more gradually acuminate and frequently strongly serrate. Sexual condition autoicous; inner perichaetial leaves erect, oblong-lanceolate, with slender serrate acumination, plicate; costa faint or distinct, double or rarely single.  Seta yellowish brown to red, 0.7--1.5 cm. Capsule yellowish brown to dark brown, inclined to horizontal, rarely suberect, varying in form and size from oblong to subcylindric, 1--2.3 mm excluding conic operculum,  usually curved, annulus 1--2 seriate; cilia of endostome 2--3.

 

Sporophytes produced summer, capsules mature June--Aug.  Rocks, most frequently on boulders, also commonly epiphytic on trees, especially tree bases, mainly in forested areas; 0--2000 m; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Ala., Alaska, Ariz. Colo., Conn., Del., D.C., Ga., Ill., Ind., Iowa, Ky., Maine., Md., Mass., Mich., Minn., Mo., Mont., N.H., N.J., N.Mex., N.Y., N.C., Ohio, Pa., R.I., S.C., S.Dak., Tenn., Vt., Va., W.Va., Wis., Wyo.; Europe; Asia.

 

Hypnum pallescens occurs from sea level to higher elevations in eastern North America, mainly in forested areas; but in western North America it is less frequent, found from near sea level to subalpine elevations of 2000 m. This species usually produces abundant sporophytes.  Hypnum recurvatum is similar in size, but the alar cells are more numerous than in H. pallescens, and the leaves of H. recurvatum are hamate to circinate, but falcate in H. pallescens; pseudoparaphyllia are foliose and mainly 4 or more cells wide in H. pallescens, while those in H. recurvatum are filamentous, often 1-seriate but generally lanceolate.  Hypnum recurvatum is mainly a calcicole while H. pallescens is usually a silicole.  For additional information, see discussion of Hypnum revolutum var. ravaudii.

 

16. Hypnum plicatulum (Lindberg) A. Jaeger, Ber. S. Gall. Naturw. Ges. 1877--78: 316.  1880

 

Stereodon plicatulus Lindberg, Acta Soc. Sc. Fenn. 10: 254.  1872; Hypnum subplicatile Limpricht; H. implexum Renauld & Cardot

 

Plants small to medium-sized, soft, often regularly pinnate, pale yellow-green to golden green, procumbent to suberect, 2--5 cm, with branches 0.2--0.5 cm, leafy main stem 0.05--0.1 cm broad. Stems yellow green or green, occasionally with tinge of brown, hyalodermous, central strand weak or absent; pseudoparaphyllia foliose, often forked with attenuate tips to lobes.  Leaves of stem curved to falcate-secund, 1--1.5 x 0.5--0.8 mm, ovate-lanceolate to narrowly triangular, curving to auriculate base and tapering to long-attenuate apex, margin plane, often toothed on auriculate portion, entire or toothed distally; costa short and double or obscure; leaf cells 50(--60)--70(--80) x 4--4.5 \um, basal cells shorter and broader, pitted alar cells 5--6, often colored, triangular to rectangular or rhomboidal, 6--15 \um long, thick walled except for the most distal one and outermost one, sometimes reduced or absent. Sexual condition dioicous (phyllodioicous).  Seta red to red-brown, 2--2.3 cm. Capsules inclined, curved, cylindric, 1.5--2 mm excluding conic operculum, 0.7--0.8 mm wide, annulus 1--2-seriate; cilia of endostome 2, as long as segments.                       .

 

Sporophytes produced infrequently in summer, capsules maturing July--Aug. Common at tree bases and up tree trunk, also on logs, over humus on cliff shelves and rocks, also on forest floor, bog margins, and in tundra; 0--2000 m; Greenland; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S., Nunavut, Ont., Que., Yukon; Alaska, Ga., Me., Mich., Minn., N.Y., N.C., Tenn., Wis.; Europe; Asia.

 

Hypnum plicatulum is a predominantly boreal to Arctic species, and is scattered in the Northern Hemisphere. This species is easy to recognize in most cases.  The frequently close-pinnate, yellowish green to golden green plants with green to yellow stems with hyalodermous, auriculate leaves with a few differentiated cells that are sometimes excavated all provide useful features.  See also discussions under Hypnum callichroum, H. hamulosum and H. holmenii.

 

17. Hypnum pratense  Spruce, London J. Bot. 4: 177.  1845

 

Breidleria pratensis (Spruce) Loeske; Stereodon pratensis (Spruce) Warnstorf; Hypnum pseudo-pratense Kindberg

 

Plants pale green to golden green, strongly glossy, soft, usually strongly complanate, with leaves sometimes falcate, medium-sized 0.5--1.5(--3) cm; leafy shoots 0.15--0.3 cm wide; erect to creeping, usually irregularly branched to unbranched, branches usually short, 0.02--0.1 cm; rhizoids rare to absent. Stems green to yellowish, epidermal cells hyalodermis, central strand present; pseudoparaphyllia foliose.  Leaves ovate, usually tapering to a broadly acute apex, 0.5--1.8 mm, curving to insertion, margins plane and entire; alar cells not conspicuously differentiated, costa short and double or absent, median cells 80--100 x 4--5 \um, at base shorter and wider, yellowish and porose, toward apex also considerably shorter. Sexual condition dioicous; inner perichaetial leaves erect, oblong-lanceolate, plicate, margins slightly toothed or entire at tip, costa obscure.  Seta reddish brown, 2--4 cm. Capsule pale brown, curved, inclined, 1--2 mm excluding conic operculum, furrowed when mature and dry, annulus 2--3 seriate; cilia of endostome 2--4.

 

Sporophytes produced infrequently, spring--summer, capsules mature July--Aug. Mainly terrestrial on moist soil in fens and calcareous sites; 0--3000 m; Greenland; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S., Nunavut, Ont., Que., Sask., Yukon; Alaska, Colo., Ill., Ky., Maine., Md., Mass., Mich., Minn., Mont., N.H., N.Y., N.C., Ohio, Oreg., Pa., S.Dak., Vt., Wis.; Europe; Asia.

 

Hypnum pratense is a temperate to boreal circumpolar species, scattered largely north of the 35° parallel of latitude, but not frequent in the Arctic. For additional comments, see discussion under Hypnum lindbergii.

 

18. Hypnum procerrimum Molendo, Flora 49: 458.  1866

 

Pseudostereodon procerrimus (Molendo) Fleischer

 

Plants robust, usually regularly and densely pinnate, suberect to procumbent, 2--8 cm, rusty brown to golden brown or occasionally dark green; branches 0.1--1.5 cm, mostly equal. Stems yellowish to brownish, with central strand, pseudoparaphyllia foliose, blunt, weakly toothed. Leaves of stem falcate-secund, ovate-oblong, gradually narrowing to a tapering acumen, margins plane and entire to sinuate, 1--1.5 x 0.5--0.8 mm, often auriculate at base, costa slender, double or absent, median cells linear-flexuose, 60 x 8 \um, somewhat pitted, cells of leaf base slender, yellowish or brownish, porose; alar cells forming a well-defined group in auriculate portion, subquadrate to subquadrate to hexagonal, 7--8 cells high along margin, and forming a triangular group of 6--8 cells in width. Sexual condition dioicous. Sporophytes unknown.

 

Terrestrial, usually in calcareous open terrain, often on rock, especially cliff ledges and bases, also tundra, open spruce forests and edges of sandy beaches; 0--1500 m; Alta., B.C., Nfld., N.W.T., Nunavut, Yukon; Alaska, Mont.; Europe (south to the Caucasus).

 

Hypnum procerrimum shows an interrupted distribution in Arctic and alpine areas of the northern hemisphere, usually found in well-drained sites.  It is a very distinctive species; some small forms might be confused with Ctenidium molluscum, but the toothed leaves and the leaf cells often with projecting upper ends separate the latter. 

 

19. Hypnum recurvatum (Lindberg & Arnell)  Kindberg, Enum Bryn. Exot. 100.  1891

 

Stereodon recurvatus  Lindberg & Arnell, Vet. Svensk Vet. Ak. Handl. 23: 149.  1890; Drepanium recurvatum (Lindberg & Arnell) Roth; Hypnum bridelianum H. A. Crum, Steere & L. E. Anderson; Hypnum fastigiatum Bridel

 

Plants yellowish to light green, blackish-brown beneath, slender, irregular to regularly 1--2(--3)- pinnate, densely to loosely (sometimes fastigiately) placed, 2--5 cm; branches unequal in length, 0.2--0.5(--0.8) cm, sometimes flagelliform, creeping and firmly affixed by rhizoids. Stems light yellow to yellowish brown, smooth, lacking hyalodermis but with weak central strand; pseudoparaphyllia frequent, possibly referable to paraphyllia, narrowly lanceolate to filamentous, rarely branched, usually with 1-seriate apex 3--6 cells in length. Leaves of stem strongly falcate-secund to circinate, 0.7--1.3 x 0.3 – 0.4mm, ovate to oblong-lanceolate, almost entire, plicate, costa indistinct, somewhat decurrent and subcordate at base, gradually narrowed to a fine acumination, margins plane or recurved near base to 2/3 or more of length, almost entire to finely serrulate, costa weak or absent, median cells 30--50 \um, sometimes longer, ca. 3 \um wide in lumen, usually thick-walled, basal cells broader and ± porose, yellowish, alar cells essentially quadrate, 4--10 in a marginal row, 10 – 15 x ca. 10 \um in lumen, thinner walled; branch leaves smaller, 0.5--1 mm, otherwise similar to stem leaves. Sexual condition. Seta reddish brown when mature, 0.7--1.5(--1.8) cm.  Capsule yellowish brown to castaneous when mature, suberect to horizontal, oblong to subcylindric, 1--2 mm excluding conic operculum, 0.4--0.8 mm thick, annulus 2-seriate; cilia of endostome (1--)2--3.

 

Sporophytes produced summer, capsules mature late summer--fall.  Obligate calcicole, usually on relatively plane surfaces of cliffs or boulders, particularly where humidity is persistent; 0-- 2000 m; Greenland; Alta., B.C., Man., N.B., Nfld., N.W.T., Nunavut, Ont., Que., Sask., Yukon; Alaska; Europe; Asia.

 

Hypnum recurvatum is widespread in the Northern Hemisphere, being more frequent in western, rather than eastern portions of the continents. This species has been confused with H. revolutum var. ravaudii, but the pseudoparaphyllia of that taxon are wide and foliose while those in H. recurvatum are lanceolate to filamentous.  The leaves of H. recurvatum are strongly falcate to circinate, while those of H. revolutum var. ravaudii are often barely falcate and sometimes straight; also alar cell differentiation in H. recurvatum is less pronounced than in the other.

 

20. Hypnum revolutum (Mitten) Lindberg, Öfr. K. Vet. Ak. Försch. 23: 542.  1867

 

Stereodon revolutus Mitten, J. Linn. Soc. Bot. Suppl. 1: 97. 1859

 

Plants rusty brownish green to yellowish green (occasionally dark green), medium-sized to slender, regularly to irregularly pinnate, or irregularly branched, erect, suberect, or creeping and firmly or loosely attached to substratum, 3--5 cm; branches 0.3--0.7 cm, the longest distant from apex, occasionally flagelliform. Stems yellow-green, lacking hyalodermis, but outermost cells often with thin walls collapsed inward, central strand weakly developed, pseudoparaphyllia foliose, lanceolate to ovate. Leaves of stem straight to falcate, secund, concave, weakly to strongly plicate, margin revolute from base to near apex, 1.1--1.8 x 0.4--0.6 mm, costa distinct to (rarely) absent, median cells short and wide 30--50 x (3--)4--5(--6) \um, thin or thick-walled, basal cells wider, thicker walled and porose sometimes yellowish, alar cells subquadrate, numerous, 8--15 in marginal row, forming clearly defined angles, 2--3 larger, hyaline, rectangular cells in decurrent portion; leaves of branches slightly smaller but otherwise similar.  Sexual condition dioicous; antheridial and archegonial plants alike; inner perichaetial leaves erect, oblong-lanceolate, plicate, acumen short, almost entire, costa indistinct.  Seta smooth, yellowish to reddish brown when mature, 1--2 cm. Capsule dull yellowish to warm brown, inclined to horizontal, oblong-cylindric, curved, 2--3 mm excluding conic operculum; annulus 2(--3)-seriate; cilia of endostome 2--3.

 

Varieties 2 (2 in flora): Greenland; North America, South America, Europe, Asia, Antarctica.

 

Hypnum revolutum is circumpolar in the Northern Hemisphere, but bipolar in distribution. It occurs at sea level in the northern portion of its range, but is most frequent at higher elevations. Strongly revolute margins are found in the genus only in H. revolutum, and the areolation in combination with the alar-cell differentiation usually make this species readily recognizable.  Creeping plants tend to be pinnate, sometimes closely and regularly; suberect plants tend to be more loosely and irregularly branched.

 

1. Plants usually of medium size, leaves plicate and strongly revolute through most of the margins . . . 20a. Hypnum revolutum var. revolutum

1. Plants usually small; leaves usually lacking plications and margins usually plane or weakly revolute at base…………………………………………….20b. Hypnum revolutum var. ravaudii

 

20a. Hypnum revolutum (Mitten) Lindberg var. revolutum

 

Plants medium sized to slender, 3--5 cm, regularly to irregularly pinnate, with branches 0.3--0.7 cm.  Leaves of stem ovate, tapering to apex, 1.1--1.8 x 0.4--0.6 mm, margins usually strongly revolute to near apex; median cells 30--40 x 4--5 \um, costa double, usually apparent.

 

Sporophytes produced summer, capsules mature July--September. Open sites, earth and rock faces, epiphytic on tree bases, logs in forest, commonly a calcicole but not confined to calcareous substrata; 0--4000 m; Greenland; Alta., B.C., Man., Nfld., N.W.T., N.S., Nunavut, Ont., Que., Sask., Yukon; Alaska, Ariz., Calif., Colo., Idaho, Mont., Nev., N.Mex., Oreg., S.Dak., Tex., Utah, Wash., Wyo.; South America (Chile); Europe; Asia; Antarctica.

 

20b. Hypnum revolutum var. ravaudii (Boulay) Ando, Lindbergia 8: 62  1982

 

Hypnum ravaudii Boulay, H.  revolutum var. dolomiticum Moenckemeyer, H. filiforme Kindb.

 

Plants smaller than in typical Hypnum revolutum, 2--3(--5) cm, usually regularly pinnate with branches 0.2--0.5 cm, rarely longer.  Leaves of stem broadly ovate-oblong, 0.5--1 mm, margins plane or less commonly revolute at base; median cells 25--40 x ca. 4 \um, costa less distinct.

 

About the same habitat, substrate, and distribution as the typical variety.

 

Hypnum revolutum var. ravaudii is scattered through the range and is seemingly infrequent. It is troublesome to determine because of its lack of the characteristic revolute margins, except sometimes near the base, and the costa is less distinct, thus it appears quite different, though smaller, from the typical variety. 

 

21. Hypnum subimponens  Lesquereux, Trans. Amer. Phil. Soc. 13: 14.  1863

 

Stereodon subimponens (Lesqereux) Brotherus

 

Plants medium sized, generally regularly and closely pinnate to plumose, soft, pale yellow green to golden green, procumbent, 2--10 cm; branches 0.2--1.5 cm, leafy main stems 0.5--1 mm broad.  Stems yellowish to pale green, hyalodermous, central strand weak or absent, pseudoparaphyllium foliose. Leaves of stem circinate-secund, 1.5--2 x 0.5--0.8 mm, not markedly curved to insertion, margins plane sinuate proximally to serrate toward apex; median leaf cells 50--65 x 4--4.5 \um, those at insertion shorter, broader and pitted, alar regions excavate, of 3--4 cells at extreme leaf angle, slightly bulging, hyaline and thin walled.  Sexual condition dioicous; inner perichaetial leaves lanceolate, weakly or not plicate, slightly toothed or entire near apex. Seta 2.5--3 cm, red-brown. Capsule cylindric, erect to suberect, 3--5 mm excluding conic to  conic or rostellate operculum; annulus 1--3-seriate.

 

Sporophytes produced spring, capsules mature May--June.  Predominantly epiphytic on living trees or on cliffs and perpendicular rock faces but persisting on decaying logs, sometimes terrestrial; 0--1500 m; B.C., N.W.T., Nunavut, Yukon; Alaska, Calif., Idaho, Mont., Oreg., Wash; e Asia.

 

Specimens of Hypnum subimponens from Arctic regions are problematic; in fact any specimens from horizontal surfaces can be difficult to place accurately.  Sporophytes are frequent only on vertical surfaces and then often are abundant.  Unlike similar species in Western North America, this species produces cylindric, erect sporangia (slightly curved below mouth when mature).  Hypnum lindbergii has falcate-secund leaves while those in H. subimponens are circinate-secund the circinate to strongly hamate  Key traits of the stem leaves separate H. subimponens from H. hamulosum, while the former is usually more than twice the size of the latter.  See also discussions of H. callichroum, H. holmenii and H. plicatulum.

 

22. Hypnum vaucheri Lesquereux, Mem. Soc. Sc. Nat. Neuchatel 3: 48.  1846

 

Hypnum subcomplexum Kindberg; H. complexum (Mitten) A. Jaeger & Sauerbeck; Stereodon vaucheri (Lesquereux) Brotherus

 

Plants brownish green to golden green, medium-sized, irregularly to somewhat regularly pinnate, creeping to suberect, usually not firmly attached to substrate, 3--6 cm; branches in a single plane, 0.3--1.5 cm. Stems yellowish brown, outermost cells not enlarged, with thin outer walls that collapse inward; with central strand; pseudoparaphyllia foliose, few, bluntly to sharply toothed on margins.  Leaves of stems erect to falcate-secund, 1.2--1.5 x 0.4--0.5 mm, ovate to broadly oblong-lanceolate, gradually to abruptly narrowed to a comparatively short acumen, broadly recurved to almost plane at proximal margin, nearly entire to serrulate distally; costa distinct, single or forked; median cells varying from short to elongate, 30--50 x (3--)4--5(--6) \um, thick and sometimes porose-walled; alar cells shorter and wider and numerous in a well-defined triangular group, with a few enlarged hyaline cells at the basal margin.  Sexual condition dioicous; inner perichaetial leaves erect, oblong-lanceolate, plicate, infrequently produced in range of the flora.  Seta yellowish to reddish brown, 1--1.5 cm. Capsule brown, inclined, somewhat curved, oblong-cylindric, 1.8--2.2 mm excluding conic operculum, annulus 2--3 seriate; cilia of endostome (1)2--3.

 

Sporophytes infrequent, capsules mature Aug.--Sept.  Generally on rock, especially calcareous rock, but also epiphytic on tree bases, mineral soil, decaying logs, mainly in sunny sites; 0--3500 m; Greenland; Alta., B.C., Man., Nfld., N.W.T., Nunavut, Ont., Que., Sask., Yukon; Alaska, Ariz., Ark., Calif., Colo., Minn., Mont., Nebr., Nev., N.Mex., N.Y., N.Dak., S.Dak., Tex., Utah, Wash., Wyo.; Mexico; South America; Europe; Asia.

 

Hypnum vaucheri is widely distributed in boreal and Arctic regions of the Northern Hemisphere. The species is readily confused with H. cupressiforme; the most reliable distinguishing feature is the blunt foliose pseudoparaphyllia of the former (filamentous to lanceolate in H. cupressiforme); in H. vaucheri the median leaf cells are often short elliptic rather than linear-flexuous, especially in leaves that are straight. Hypnum vaucheri is predominantly continental in distribution in North America, while H. cupressiforme is frequent near the coasts.

 

EXCLUDED TAXA

 

Hypnum geminum (Mitten) Lesquereux & James does not appear to be a species of Hypnum as treated here.  The type specimen is extremely small and difficult to interpret. It is possibly Isopterygiopsis pulchella.

 

Hypnum fertile Sendtner as treated previously in North America has been shown to be H. fauriei Cardot  See discussion of that species.

 

Hypnum canariense (Mitten) A. Jaeger (Hypnum uncinatulum Juratzka), though noted by A. J. Grout (1932) presumably from Newfoundland, is not in North America. Grout appears to have based the record on H. waghornei Kindberg, in which the type contains a mixture, none of it Hypnum.  Grout did not see authentic material, and appears to have followed Kindberg in Macoun’s Catologue Iof Canadian Plants, Part VII (1902).

 

Hypnum obsoletinerve Kindberg is clearly not Hypnum.

 

OTHER REFERENCES

 

Ando, H.  1989.  Studies on the genus Hypnum Hedw. (VI).  Hikobia 10: 269--291.

Grout, A. J.  1932.  Moss Flora of North America 3: 127. Newfane. 3 vols.

 

Illustrations, click here