BFNA Title: Pseudoleskeella
XX. PSEUDOLESKEELLA Kindberg, Gen. N.-Amer. Bryin. 20. 1897 * (Latin, pseudo, false, and Leskeella)
John R. Spence
Plants prostrate, in thin mats or patches. Stems slender, creeping, irregularly branched, secondary branches appressed to ascending or erect, sometimes becoming flagelliform at tips, paraphyllia absent, rhizoids in clusters arising from base of leaves, older primary stems becoming stoloniferous. Leaves of stems and branches differentiated, primary stem leaves ovate to lanceolate, symmetric or asymmetric, appressed to erect when dry, catenulate or not, erect spreading when wet; lamina smooth to sometimes plicate on either side of costa, apex abruptly to gradually acuminate or subulate, tips of leaves, especially branch leaves, often recurved or falcate, margins entire to serrulate distally, plane or recurved proximally; costa moderately strong and percurrent, to short, single or double, not sinuose, sometimes somewhat obscure distally; mid-laminal cells isodiametric to 2--3:1, rarely to 6:1, smooth, firm- to thick-walled, alar cells not well differentiated, generally in small groups of quadrate to short-rectangular cells, laminal cells in acumen somewhat longer than cells below, rarely weakly prorate; secondary branch leaves smaller, more ovate, mid-laminal cells mostly shorter than stem leaves, costa typically weaker than stem leaves; older stoloniferous leaves distant, often denuded, scale-like, sometimes hyaline. Specialized asexual reproduction absent. Sexual condition dioicous; perichaetial leaves pale translucent, longer and more acuminate, appressed to rarely recurved. Capsule ovate to cylindric, erect, inclined to patent, symmetric or more commonly curved-asymmetric, operculum conic, short-rostrate; peristome double, exostome teeth lanceolate or linear-lanceolate, endostome of moderately high basal membrane, free, segments slender, lanceolate to filiform, cilia present, generally well developed. Spores small, 8--20 \um, finely papillose.
Species 6 (4 in flora): Northern Hemisphere, mostly in cool-temperate, montane, Arctic-alpine and boreal-temperate regions.
Pseudoleskeella consists of small slender
appressed plants with smooth leaf cells, no paraphyllia, and a relatively
weak costa, often forked. Occasionally some cells of the lamina in the distal
portion become weakly prorate. However, the taxa morphologically seem to be
quite different from each other beyond these few shared traits. Molecular studies have shown that P.
serpentinensis is not related to the other species, rather it appears to
be closest to Heterocladium (M. S. Ignatov et al. 2007). There are two
morphological groups, species with appressed leaves with moderately strong
costae (P. arizonae, P. serpentinensis, P. sibirica), and those with
catenulate leaves and short typically forked costae (P. catenulata, P.
papillosa, P. tectorum). Following P. Wilson and D. H. Norris (1989), P.
catenulata and P. papillosa are excluded from
REFERENCES: Flowers, S. 1973. Mosses of
1. Leaves more or less catenulate; costa short, typically double, not reaching mid-leaf, plants very small and tightly appressed to substrate ...............4. Pseudoleskeella tectorum
1. Leaves appressed but not catenulate, costa typically single, mostly to mid-leaf or sometimes percurrent, rarely forked, plants small to medium, not tightly appressed to substrate.
2. Plants dark green to yellow-green; leaves distinctly plicate, base cordate and
flared, margins revolute to beyond mid-leaf, distinctly serrulate distally
....................................................................................1. Pseudoleskeella arizonae
2. Plants green to often reddish-green; leaves not obviously plicate, base not
flaring or cordate, margins plane throughout to revolute proximally, distal
margins more or less smooth or finely serrulate.
3. Stem leaves lanceolate, more or less straight, gradually tapered to apex; not long drawn out or awn-like, costa strong, mostly beyond mid-leaf, rarely forked; plants orange-red to green, laminal cells of mature leaves of ultimate branches thin-walled.......2. Pseudoleskeella rupestris
3. Stem leaves ovate-lanceolate, homomallous, abruptly tapered to apex, sometimes apex long drawn out and awn-like, costa variable, from short and forked to single and reaching mid-leaf or sometimes beyond; plants dull red-brown or green-brown; laminal cells of mature leaves of ultimate branch leaves incrassate ........3. Pseudoleskeella serpentinensis
Pseudoleskea arizonae R. S. Williams, Bryologist 33: 20, figs. 1--10. 1930; Lescuraea arizonae (R. S. Williams) P. Wilson & Norris; Leskeella arizonae (R. S. Williams) Flowers.
Plants green to yellow-green, older stems golden. Stems weakly appressed to substrate, irregularly branched, secondary branches common, curved to erect, not clustered, sometimes becoming flagelliform, older primary stems becoming stoloniferous. Leaves of primary stems 0.6--1.5(--2) mm, length to width ratio typically 3:1, ovate, not catenulate when dry, erect-spreading wet, concave, strongly and distinctly 2-plicate, gradually or abruptly narrowed into short to medium-length acumen, not homomallous, tips often falcate, margins distinctly serrulate distally, recurved to mid-leaf or beyond on one or both sides, costa strong, reaching mid-leaf to percurrent, single, median laminal cells rhomboidal, short, 2(--3):1, firm walled but not incrassate; secondary branch leaves smaller, 0.4--0.8 mm, ovate to ovate-lanceolate; stoloniferous leaves broadly ovate or suborbicular. Seta 1--2 mm, red-brown, straight to flexuose. Capsule 1--2 mm, inclined, brown, subcylindric, asymmetric. Spores 10--16 \um.
Capsules mature summer. Locally common on shaded calcareous rock
or less commonly on shaded tree bases or wood or rarely soil over rock;
Pseudoleskeella arizonae is somewhat anomalous in the genus, and has been moved among four different genera since its description. It is very similar to a small Pseudoleskea, but differs in the lack of paraphyllia. However, there are collections of other species of Pseudoleskea that occasionally produce few if any paraphyllia. The leaves are also similar to Pseudoleskea. Molecular data is probably needed to determine its correct placement. It may represent a new genus.
2. Pseudoleskeella rupestris (Berggren) Hedenäs & Soderström, Lindbergia 17: 64. 1991 
rupestris Berggren, Acta Univ. Lund. 2 Afd. 3(7): 9, figs.
10--13. 1866; Pseudoleskeella sibirica (Arnell) P. Wilson & Norris; Leskeella
nervosa (Bridel) Loeske var. sibirica (Arnell)
Plants green to red-green or orange-green. Stems somewhat loosely appressed to substrate, irregularly branched, secondary branches common, curved to erect, sometimes becoming flagelliform, older primary stems becoming stoloniferous. Leaves of primary stems 0.5--1.5 mm, length to width ratio typically 3:1, broadly lanceolate to ovate-lanceolate, not or weakly concave, not plicate, narrowed into slender straight acumen, irregularly twisted when dry, distal margins entire or weakly serrulate, costa strong, to mid-leaf or extending into acumen, somewhat flared in acumen, rarely forked near tip, median laminal cells 2--3:1, incrassate; secondary branch leaves smaller, 0.6--0.1.2 mm, ovate-lanceolate, stoloniferous leaves broadly ovate-lanceolate to ovate. Seta 1--3 mm, brown or red-brown, stright to flexuose. Capsule erect, 2--3 mm, brown cylindric, symmetric. Spores 8--12 \um.
Sporophytes unknown in
Pseudoleskeella rupestris is similar to Leskeella
nervosa, and should probably be moved to that genus. This is supported by
the report in W. A. Weber and R. C. Wittmann (2007) of plants from
3. Pseudoleskeella serpentinensis P. Wilson & Norris, Bryol. 92: 391-392. 1989
Plants red, red-brown to green. Stems loosely appressed to substrate, irregularly branched, secondary branches common, appressed, not clustered, sometimes becoming flagelliform, older primary stems becoming stoloniferous. Leaves of primary stems 0.3--1.5 mm, ovate to lanceolate, not catenulate when dry, erect-spreading wet, weakly concave, not or weakly plicate, abruptly narrowed into short to medium-length acumen, homomallous, tips sometimes falcate, margins finely serrulate distally, plane or rarely recurved proximally, costa moderately strong, typically to mid-leaf, single or occasionally forked above, somewhat flared in acumen base, median laminal cells short, 2:1, incrassate, secondary branch leaves smaller, 0.3--1 mm, ovate to sub-orbicular, not catenulate, laminal cells incrassate; stoloniferous leaves scale-like, sometimes hyaline, ovate or orbicular; median lamina cells elongate, 3--6:1. Sporophyte unknown.
Rare, on serpentine rock, 50--1000 m,
Pseudoleskeella serpentinensis is a recently described endemic species known only from sterile and female plants. Superficially, it looks like a small version of Rigodiadelphus baileyi, but molecular data suggest a placement near Heterocladium. The reddish color, elongate laminal cells of the stem leaves, the serrulate distal leaf margins, and homomallous drawn-out leaf tips are diagnostic. On fertile plants the perichaetial leaves are also recurved, whereas they are erect to appressed in the other species. It was originally determined as P. catenulata, but P. Wilson and D. H. Norris (1989) showed that it was a distinct undescribed species.
4. Pseudoleskeella tectorum (Funck ex Bridel) Kindberg ex Brotherus, Die Nat. Pfl. I (3): 997. 1907
Hypnum tectorum Funck ex Bridel, Bryol. Univ. 2: 582. 1827; Pseudoleskea tectorum (funck ex Bridel) Schimper
Plants dark olive-green or rarely yellow-green. Stems tightly appressed to substrate, irregularly branched, secondary branches common, appressed, not clustered, sometimes becoming flagelliform, older primary stems becoming stoloniferous. Leaves of primary stems 0.4--1.2 mm, ovate, length to width ratio 1.5--2:1, more or less catenulate when dry, erect-spreading wet, concave, not plicate, abruptly narrowed into short acumen, not homomallous, tips sometimes falcate, margins smooth, entire or rarely recurved proximally, costa weak, not reaching mid-leaf, single, forked, double or sometimes absent; median laminal cells short, 1--2(--3):1, firm walled but not incrassate; secondary branch leaves smaller, 0.4--0.8 mm, ovate to sub-orbicular, catenulate; stoloniferous leaves broadly ovate or suborbicular. Seta 1--2 mm, red-brown, straight to flexuose. Capsule 1.5--2.5(--3) mm, inclined, brown, subcylindric, asymmetric. Spores 10--18 \um.
Capsules mature summer. Common on shaded calcareous rock or rarely
on shaded tree bases or wood; 0--4000 m;
The dark green tightly appressed thin mats, catenulate leaves, and weak costa are diagnostic of Pseudoleskeella tectorum. Mats this species can be become quite extensive over time, covering the faces and overhangs of shaded boulders and cliffs.