Polytrichum jensenii

I. Hagen

Meddel. Grønland 15: 444. 1897,.

Synonyms: Polytrichum commune var. jensenii (I. Hagen) Mönkemeyer Polytrichum commune var. diminutum (I. Hagen) D. G. Long Polytrichum commune var. yukonense (Cardot & Thériot) Frye Polytrichum yukonense
Treatment appears in FNA Volume 27. Treatment on page 137. Mentioned on page 134.

Plants rather fragile, forming extensive green carpets or as scattered stems among other bryophytes. Stems 3–12 cm. Leaves (4–) 6–10 mm, ± distant, not crowded; closely appressed, straight or erect-spreading and weakly flexuose when dry, erect-spreading to widely spreading or weakly recurved when moist, caducous at the base of blade; sheath short, scarcely broadened and rather weakly differentiated; marginal lamina narrow, 2–3 cells wide, erect to somewhat involute towards the apex, entire to finely and obscurely serrulate from the middle upwards, the teeth rather weak and distant; costa smooth abaxially, ending in a short, weakly toothed tip; lamellae crenulate in profile, 8–12 cells high, with paired, projecting knobs along the margins, the marginal cells in section rather narrow, retuse, thick-walled, brownish, smooth; sheath cells rather short rectangular, 60–90 × 15–22 µm; cells of the marginal lamina ± isodiametric; perichaetial leaves with sheathing bases usually hidden by upper stem-leaves. Seta 1.5–4.5 cm, brownish. Capsule 2.5–3.5 mm, sharply 4–5-angled, short rectangular to cubic.


Habitat: Periodically flooded areas, bogs, sedge meadows, margins of lakes, streams and rivers
Elevation: low to moderate elevations (0–1500 m)

Distribution

V27 167-distribution-map.gif

Greenland, Nfld. and Labr. (Labr.), N.W.T., Nunavut, Que., Yukon, Alaska, Wyo., Arctic Europe, Asia (n Russia)

Discussion

Polytrichum jensenii is a widely distributed plant of the high Arctic, with a sporadic disjunct occurrence southward, where its distribution is poorly documented. In Nunavut, it is known from Melville Island. In arctic America it replaces P. commune north of the tree line (D. G. Long 1985, as P. commune var. diminutum), and is notable for its rather fragile texture, entire to weakly toothed leaf margins, and caducous leaf blades. The marginal cells of the lamellae are similar to those of P. commune. Forms of P. swartzii have entire or nearly entire, caducous leaves, but the marginal cells of the lamellae are rounded quadrate and thin-walled, absent the distinctive, thickened knobs of P. jensenii and P. commune. Genetic evidence may support the recognition of P. jensenii as a distinct species (G. S. Derda and R. Wyatt 1999).

Selected References

None.

Lower Taxa

None.

"broadened" is not a number."wide" is not a number."broader" is not a number.

... more about "Polytrichum jensenii"
prominent +
Gary L. Smith Merrill +
I. Hagen +
flexuose +
erect-spreading +  and widely spreading or weakly recurved +
weakly-developed +
abrupt +, crisped +  and undulate +
abbreviated +
firm-textured +
overlapping +
isodiametric +, serrulate +  and entire +
monoicous +, dioicous +, sexual +  and vegetative +
sinuate;fiberlike;elongate;less isodiametric;transversely elongate-hexagonal +
sparsely ciliate;smooth +
cucullate +
reddish +  and purplish brown +
horizontal;suberect +
rectangular to cubic +  and 4-5-angled +
0.25 cm2.5 mm <br />0.0025 m <br /> (0.35 cm3.5 mm <br />0.0035 m <br />) +
extensive +
short-excurrent +
prolonged +
toothed +
undifferentiated +
Greenland +, Nfld. and Labr. (Labr.) +, N.W.T. +, Nunavut +, Que. +, Yukon +, Alaska +, Wyo. +, Arctic Europe +  and Asia (n Russia) +
low to moderate elevations (0–1500 m) +
bulging-mammillose +
scabrous +, mammillose +  and smooth +
Periodically flooded areas, bogs, sedge meadows, margins of lakes, streams and rivers +
closely-spaced +
photosynthetic +
8 +  and 12 +
crenulate +
not crowded +  and distant +
0.4 cm4 mm <br />0.004 m <br /> (0.6 cm6 mm <br />0.006 m <br />) +
straight +
0.6 cm6 mm <br />0.006 m <br /> (1 cm10 mm <br />0.01 m <br />) +
membranous +
alternating +
1(-3)-stratose +
cuticular-papillose +  and smooth +
dissected +
shape +  and size +
dioicous +  and sexual +
inflexed +  and erect +
toothed +  and plane +
pigmented +  and pale +
single +  and 64 +
slit-like +  and circular +
Meddel. Grønland +
underground +
differentiated +
1.5 cm15 mm <br />0.015 m <br /> (4.5 cm45 mm <br />0.045 m <br />) +
hyaline-margined +
rectangular +
differentiated +
broadened +
rhizoidous +, bracteate +  and leafy +
wooly-tomentose +
3 cm30 mm <br />0.03 m <br /> (12 cm120 mm <br />0.12 m <br />) +
Polytrichum commune var. jensenii +, Polytrichum commune var. diminutum +, Polytrichum commune var. yukonense +  and Polytrichum yukonense +
Polytrichum jensenii +
Polytrichum +
species +
toothed +
unjointed +
loose +  and compact +