Illustrated Key to Liverwort Genera of Oregon. David H. Wagner, Northwest Botanical Institute, P.O. Box 30064, Eugene, OR 97403
Introduction
This key to liverwort genera is extracted from "Guide to the Liverworts of Oregon" (Wagner 2013), a web formatted, electronic document for identifying the liverworts found in Oregon. The first, text-only, version of this key was published nearly thirty years ago (Wagner, 1984). An illustrated key developed for class use appeared in a document treating species of conservation concern in the region (Christy and Wagner 1996). Work on the digital version which includes keys to species, "Guide to the Liverworts of Oregon," began in 2002. The decision to focus on a digital guide was based on two ideas. First, it allows incorporating hundreds of color photomicrographs, impossible in a traditional book printed on paper. Second, an electronic, HTML version of a dichotomous key has significant advantages over a printed key. The web format assures that a user is always taken to the proper destination based on the choice of lead in a couplet. It allows step by step backtracking through the key, instant return to the beginning, and thumbnail hot links to images. The structure of the work makes it an excellent learning tool as well as a way to identify liverworts.
This key can be used profitably as a companion to the keys for California liverworts and hornworts by Doyle and Stotler (2006) and the excellent treatment of liverwort genera of the western states by Schofield (2002). For identification to species that follows upon this key to genera, see "Guide to the Liverworts of Oregon" (Wagner 2013), available for purchase at fernzenmosses.com.
How to use the Key
Each page in this key is a couplet with two contrasting leads. Decide which lead best fits the specimen being studied. Click on the highlighted part of the lead to go to the next couplet or to a genus. If the genus is known to have only one species in Oregon, the full species name is given.
Breadcrumbs
At the top of every page of the key there is a line of breadcrumbs. This is a series of links to the leads in each previous couplet taken to arrive at this page. It is a shorthand record of choices made. One can go back to any step in the keying process by clicking on the appropriate phrase in the breadcrumb trail. Clicking on the first breadcrumb will lead back to the start of the key. There is also a "GO BACK ONE STEP" link at the bottom of each page to backtrack through the keying process one step at a time.
Thumbnails
All images on the key pages are thumbnails. Click on a thumbnail to see a large image. They have been saved at 1000 pixels high to retain reasonably good resolution for viewing and printing. Use your back arrow ("Show the previous page") to return to the page on which the thumbnail was located.
Shortcuts to Distinctive Groups
There are genera which are traditionally clustered together in keys because they share certain easily recognized, diagnostic characters. These are listed here with links to the couplet where the treatment of that group begins. A botanist experienced with liverworts will start directly with one of these groups by using the hotlinks below. A beginner would do well to learn to recognize them on sight. Note that each of these groups is both inclusive (every liverwort genus with the characters defining the group can be identified by starting with the first couplet of that group) and exclusive (no liverwort genus without the defining characters will be found in that group). For this reason, the shortcuts list can be considered a polyclave or multi-access key.
LEAF LOBES CILIATE [Couplet 4]
LEAVES COMPLICATE-BILOBED; SMALL DORSAL LOBE [Couplet 8]
OILBODIES ABSENT OR SOLITARY [Couplet 16]
LEAVES COMPLICATE-BILOBED; LOBULE VENTRAL [Couplet 21]
LEAVES INCUBOUS; NO LOBULE [Couplet 23]
ISOPHYLLOUS (THREE EQUAL ROWS OF LEAVES) [Couplet 25]
ROUND, SUCCUBOUS LEAVES [Couplet 28]
LOBED, SUCCUBOUS LEAVES [Couplet 37]
TINY SHOOTS (AVERAGE <0.5 mm WIDE) WITH BILOBED LEAVES [Couplet 47]
THALLOSE LIVERWORTS [Couplet 62]
THALLOSE WITH HOMOGENEOUS TISSUE [Couplet 63]
THALLOSE WITH DIFFERENTIATED TISSUE [Couplet 70]
Literature cited
Christy, J.A. and D.H. Wagner. 1996.
Guide for the Identification of Rare, Threatened or Sensitive Bryophytes in the Range of the Northern Spotted Owl, Western Washington, Western Oregon, and Northwestern California. USDI Bureau of Land Management, USDA Forest Service, The Nature Conservancy, and Northwest Botanical Institute, Portland, Oregon, U.S.A.Doyle, W.T. and R.E. Stotler. 2006.
Contributions toward a bryoflora of California III. Keys and annotated species catalogue for liverworts and hornworts. Madroño 53: 89-197.Wagner, D.H. 1984.
Artificial key to the genera of liverworts in Oregon. Evansia 1: 13-22.Wagner, D.H. 2013.
Guide to the Liverworts of Oregon. Privately published, Northwest Botanical Institute, Eugene, Oregon. Perpetual digital publication. 419 pages, 750 color pictures as of 1 April 2013.Schofield, W. 2002.
Field Guide to Liverwort Genera of Pacific North America. University of Washington Press, Seattle, Washington, U.S.A.
Copyright 2013 Northwest Botanical Institute