Guide to Liverworts of Oregon: Key to Porella 1
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1b plants leafy > 3b leaves not divided, not ciliate > 6a oil bodies 2+ or unknown > 7b no small dorsal lobe > 10b leaves incubous > 20a lobule present > 21b underleaves present > 22b flap like lobule > Porella
This genus has three very common species in Oregon: P. navicularis, P. cordaeana, and P. roellii (in that order of abundance). Porella bolanderi is rare in the state but has been reported rather frequently (and mostly inaccurately). It looks most like P. cordaeana, from which it can be separated by a negative iodine-potassium iodide (IKI) reaction. Porella cordaeana is the only species in our region with a positive test--its cells turn dark purple when treated with the standard stain reagent. The color reaction in this case is not due to starch but to a flavonoid, saponarin. The peppery taste of P. roellii is unmistakable in fresh material but diminishes after the specimens have been in a packet for a year. Despite numerous reports of P. platyphylla ( or P. platyphylloides) from Oregon, all specimens examined to date have proven to be P. navicularis, a morphologically plastic taxon, or in a few cases one of the other species treated here.
Porella roellii,
1a Plants with peppery-acrid taste; ventral lobes of lateral leaves narrowly triangular, mostly plane; ventral lobe midline parallel to the stem on side branches; decurrent portion of underleaves and ventral lobes crispate-convoluted, often developed into paraphyllia; perianth mouth broad, toothed on margin; IKI negative; common and widespread in Oregon
Porella roellii
Porella navicularis
1b Plants with aromatic taste but not peppery-acrid; ventral lobes of lateral leaves ovate or broadly triangular; ventral lobe midline angled away from the stem on side branches; decurrent portion of underleaves and ventral lobes plane (but sometimes toothed); perianth mouth narrow, edentate; IKI negative or positive (taste, perianths, and IKI reaction unknown in P. fauriei from Oregon)
(Couplet 2)