Branch leaves distinctly 5-ranked in and below capitulum;

fascicles with 4–5 branches in total, of which 2–3 are spreading; stem leaves triangular-acuminate, with wide zone of elongate cells at base; stem hyalodermis with

scattered pores or pseudopores; sclerodermis green with red spots. . . .Sphagnum quinquefarium (rr) – Branch leaves not distinctly 5-ranked outside capitulum;

fascicles with 3–4 branches in total, of which rarely more than 2 are spreading; stem hyalodermis without pores, but sometimes with pseudopores; sclerodermis reddish or brownish even in otherwise green plants. . . .18 18 Stem leaves 1.5–1.7 mm long, contracted into tubulose apex, at base with narrow to moderately widened zone of elongate cells, hyalocysts usually without fibrils, several times septate; plants lustrous when dry, violet reddish. . . .

. . . .Sphagnum subnitens (n.s.)

– Stem leaves 0.9–1.4 mm long, not contracted into tubulous apex, triangular to triangular-lingulate, often rounded at apex, at base with widened zone of elongate cells, hyalocysts usually with fibrils in apical part of stem leaf, ± septate, but rarely more than once; plants not lustrous when dry, reddish, often in compact tufts. . .Sphagnum capillifolium (r) 19(5) Stem leaves to 1.6 mm long, at apex with a cleft of 1/3 of leaf

length; branch leaves to 3 mm long; very robust, green plants. . . .Sphagnum riparium (rr) – Stem leaves without apical cleft. . . .20 20 Stem leaves triangular-lingulate to lingulate, rounded at apex. . . .21 – Stem leaves triangular, narrowed above, rounded or acute at apex. . . .23 21 Branch leaf hyalocysts with numerous dorsal pores arranged in 1 or 2 rows, pores often indistinct and visible only after extensive staining; stem leaves > 1 mm long;

robust plants. . . .Sphagnum obtusum (rr) – Branch leaf hyalocysts with few pores in the cell corners only. . . .22 22 Stem leaves 1 mm long or little longer, longer than wide;

axes of branches and stems pale; robust plants. . . .

. . . .Sphagnum flexuosum (rr)

– Stem leaves mostly < 1 mm long, as long as wide; axes of branches and stems often pink; small to medium sized plants. . . .Sphagnum angustifolium (r) 23 Stem leaves 1–2 mm long, triangular, longer than wide;

branch leaves > 4 times as long as wide; chlorocysts

trapezium-shaped in transverse section, exposed on both sides. . . .Sphagnum cuspidatum (rr) – Stem leaves < 1 mm long, triangular, as long as wide, apex cuspidate; chlorocysts in transverse section widely exposed on dorsal side, narrowly exposed on ventral side. . . . . . . .Sphagnum fallax (r)

Note: A useful way to distinguish S. fallax from S. cuspidatum in the field is to tear off a capitulum and inspect the pendent branches at its underside:

these are in pairs, whitish and downwards pointing in S. fallax, whereas in S. cuspidatum they are greener and stick out sideways (Godfrey and Hill 2012).

24(5) Plants mostly bright green to greenish yellow; branch leaves with apices distinctly reflexed, 1.7–3.1 × 1.0–1.8 mm;

hyalocysts elongate throughout the leaf, distinctly wider in basal part. . . .Sphagnum squarrosum (r) – Plants yellowish brown, rarely pure green; branch leaves

usually imbricate, apices rearly reflexed, 1.0–2.3 × 0.5–1.2 mm, hyalocysts shorter towards apex, of equal width throughout leaf. . . .Sphagnum teres (rr) Key to the varieties of Andreaea rupestris

References: Murray (1987, 1988)

– Leaves shortly and bluntly apiculate, 0.7–1.5 mm long;

plants to 2 cm high; papillae on dorsal side of leaves less than twice as high as wide. . . .

. . . .Andreaea rupestris var. rupestris

– Leaves narrow, longly pointed, to 2 mm long; plants to 3 cm high; papillae on dorsal side of leaves more than twice as high as wide. . . .Andreaea rupestris var. papillosa Key to species of Polytrichaceae

For an auxiliary key for sterile plants of Polytrichastrum, Polytrichum and Pogonatum, see below

1 Costa narrow (< 1/5 leaf width), leaves therefore translucent, crispate when dry, bordered by long narrow cells, transversely undulate when moist; capsule usually inclined (nearly erect in A. flavisetum), with long operculum and cucullate, hairless calyptra. Atrichum. . . .2

– Costa wide, filling upper part of leaf, leaves therefore opaque, not changed when dry, whithout border of narrow long cells, never transversely undulate; usually leaf base sheathing; capsule with campanulate, usually hairy calyptra. . . . . .4 2 Leaves about 1 mm wide; lamina cells 10–16 (20) µm in diameter; leaves ± taut, not much transversely undulate;

lamellae 5–6 (7) in number, 6–9 cells high; spores 12–14 µm

. . . .Atrichum angustatum (w)

– Leaves 1.5–2 mm wide; lamina cells 20–30 (50) µm in diameter; leaves distinctly transversely undulate; lamellae 4–5 (6) in number, to 5 cells high; spores 16–20 µm. . . .3 3 Autoicous (antheridia terminal on first year's growth, archegonia terminal on second year's growth); sporophytes mostly single, seta red, capsule red brown, inclined. . . . . . . .Atrichum undulatum (c) – Paroicous (antheridia terminal, archegonia outside perigonial leaves, stem continuing growth for 2 or more years, so that persistent setae appear lateral); often several sporophytes in a single perichaetium, seta yellowish (straw-coloured to reddish-yellow), capsule dark purple to reddish, narrow, almost erect. . . .Atrichum flavisetum (Atrichum haussknechtii, A. undulatum var. gracilisetum) (rr) 4(1) Capsule without apophysis and stomata, terete. Pogonatum

. . . .5 – Capsule with apophysis and stomata, 4–6-angled or terete. . .7 5 Plants bluish-green, > 2 cm tall, often branched or with subterranean stolons; protonema not persistent; uppermost cells of lamellae papillose, wider than tall in cross section. . . .

. . . .Pogonatum urnigerum (w)

Note: for the difference between this species and Polytrichastrum alpinum, see the note under that species.

– Plants dark green, < 2 cm tall, unbranched; protonema persistent; uppermost cells of costal lamellae smooth. . . .6 6 Leaf margins serrate to mid-leaf or along whole blade;

capsule (without lid) (1.8) 2.8–3.2 (3.8) mm long, shortly cylindrical, 2–3 times as long as wide, exothecial cells with coarse prominent mamillae. . . .Pogonatum aloides (w)

– Leaf margins serrate only at apex; capsule (without lid) to 2.3 mm long, ovoid to almost globose, 1–1.5 times as long as wide, exothecial cells finely papillose. . . . . . .Pogonatum nanum (r) 7 Capsule cylindrical, rounded; uppermost cells of costal lamellae papillose, taller than wide in cross section. . . .

. . . .Polytrichastrum alpinum (Polytrichum alpinum) (n.s.)

Note: Pogonatum urnigerum also has papillose end cells of lamellae, but these are wider than tall. Other differences between these two species which share also round, not angled capsules, are: (i) colour: dull green in P. alpinum, glaucous green in Pogonatum urnigerum; (ii) length of sheathing part of leaf: 24–30% of total leaf length in P. alpinum, to 22%

in Pogonatum urnigerum; (iii) stomata lacking in capsules of P. urnigerum, stomata present at base of urn in P. alpinum.

– Capsule angled; uppermost cells of costal lamellae smooth.

Polytrichum. . . .8 8 Leaf margins sharply serrate in upper part of leaf, plane when moist. . . .9 – Leaf margins almost entire (except at tip), involute when moist. . . .12 9 Uppermost cells of costal lamellae furrowed or flat in transverse section, at least in part. . . .10 – Uppermost cells of costal lamellae all rounded. . . .11 10 Uppermost cells of costal lamellae all grooved. . . .

. . . .Polytrichum commune (r)

– Uppermost cells of costal lamellae variable in shape, some asymmetric, some grooved, some flat-topped (especially in median part of costa), some rounded (especially in marginal part of costa). . .

. . .Polytrichum perigoniale (P. commune var. perigoniale) (r)