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A Liverwort - Porella navicularis
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General Description
GROWTH FORM : Leafy.PLANTS : Glossy, yellowish-green to brown plants that form dense, coarse mats. Shoots are 1-2 times pinnate and up to 12 cm long and 1.5 to 3 mm wide. Male plants have branches that are short and lateral, 1.5-2.5 mm long. Female plants have branches that are very short, lateral, and with a few smaller leaves at base. Perianth is broadly obovoid, 3-5 mm long, 2.2-4.0 mm wide. When mature the perianth tip is dorsiventrally compressed and bent toward the ventral side and the mouth is wide, deeply 2-lipped, and toothless. UPPER-LEAVES : Dorsal leaves are flexed downward, and have entire margins. Lobules (ventral upper-leaves) are oval to ovate, two-fifths to one-half the width of the dorsal leaf. The margins area entire and recurved, and when dry the apex is commonly recurved. UNDER-LEAVES : Imbricate, oblong-quadrate in shape, and with a fairly long decurrent leaf. The apex is rounded and sometimes recurved. Margins are entire at the under-leaf’s base. Trigones (triangular-shaped corner thickenings of the cells walls) are large and bulging, such that they bulge inwards on the cells.
Diagnostic Characteristics
Porella navicularis * Size: Plants are glossy with shoots 1.5-3 mm wide.
* Trigones present - cell corners have the walls bulging inward.
* Lobules are neatly and noticeably revolute; nearly as wide as the under-leaves, and with an axis that diverges from the stem.
* Under-leaves are entire.
* Plants do not turn violet with iodine potassium-iodide (IKI).
* Plants are strongly aromatic, but not acrid.
Porella cordaeana * Size: Shoots are 3-4 mm wide.
* Lobules are about half the width of the under-leaves.
* Under-leaves do not overlap, leaving stretches of the stem visible.
* Decurrent portion of under-leaves are ruffled with a few teeth along the bases.
* Plants turn violet with IKI.
Porella platyphylla * Under-leaves overlap.
* The lobule margins are slightly revolute.
* Decurrent portion of under-leaves have smooth, slightly revolute margins.
* Plants turn violet with IKI.
Porella roellii * Cells walls of the leaves without their corners bulging into the cell lumens.
* Under-leaves about twice as wide as the lobules.
* Lobules are oriented parallel to the main stem, and are much narrower than the under-leaves.
* Plants do not turn violet with IKI.
* Plants taste peppery when fresh (David. H. Wagner personal communication).
The Type specimen (from which the species was first described) was collected in the USA.
“West Coast hb Hooker”
Sources: Piippo and Norris 1996; Paton 1999.
Range Comments
Endemic to western North America: Alaska, British Columbia, California, Idaho, Montana, Oregon, Washington, and Wyoming (Hong 1987).
Habitat
On trees, logs, and rocks within moist, shaded sites (Hong 1976).
Reproductive Characteristics
Dioicous - separate male and female liverwort plants.
Stewardship Responsibility
Threats or Limiting Factors
Threats to Porella navicularis populations include loss of shade trees by forest fires and logging that degrades the habitat.
References
Literature Cited AboveLegend:
Additional ReferencesLegend: Do you know of a citation we're missing? Northwest Science : Official Publication of the Northwest Scientific Association. 76: 271-285.
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