Introduction and Explanation
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This key is a regional summary and reworking of the treatment of Racomitrioideae in the Flora of North America (FNA), v. 27 (Ochyra and Bednarek-Ochyra 2007). These authors have divided the traditional genus Racomitrium into four genera that reflect reasonably natural groupings. Whether or not these are monophyletic clades that will gain acceptance at generic rank awaits phylogenetic data from cladistic and/or molecular analyses. For the field botanist, for whom the primary issue is confident identification of species, it remains convenient to consider them together, as in the traditionally circumscribed genus. This is particularly true when dealing with identification based mainly on vegetative characters. The field botanist often does not have reproductive structures available and vegetative characters overlap among the segregate genera. The key that forms the core of this guide relies almost completely on leaf characters. To avoid confusion between Racomitrium in the traditional, broad sense and Racomitrium in the narrow sense (with only one species) I will refer to them as racomitriums. When I write racomitriums, I mean Racomitrium in the broad sense.
This key should work well in California but some species known to occur in Washington are not included. Based on the catalog of California mosses by Norris and Shevock (2004a), the distributions given in the Flora of North America, and personal experience, I have selected 20 species to include in this guide. The list includes several species which have not yet been found in Oregon but whose occurrence in adjacent states indicates they are likely to grow here. There is much exploration to be done.
A current understanding of the racomitriums of Oregon could begin with Elva Lawton, who studied the genus thoroughly in preparation for her manual on mosses of the Pacific Northwest (Lawton 1971). Her work continues to be very useful and fortunately remains in print. (Note: she used the spelling Rhacomitrium, a common, older, but now rejected variant spelling of the genus name.) She wrote quite usable keys which, however, lumped together a number of forms now recognized as separate species. People trained on Lawton's keys should be aware that there are now several species recognized for each of three species: Racomitrium canescens, R. heterostichum, and R. sudeticum. The person most responsible for clarifying species distinctions in these groups is Arne Frisvoll, whose work stands today as benchmark of careful work (Frisvoll 1983, 1988). Building on this standard of critical study, Halina Bednarek-Ochyra and her husband, Ryszard Ochyra, have described two new species from our flora and, in providing a treatment for the Flora of North America, have established the most recent assessment of the racomitriums (Ochyra and Bednarek-Ochyra 2007). This guide has been created with the bryologically tuned field botanists of the Pacific Northwest in mind. I hope that it will encourage them to continue expanding our collective knowledge of the bryophytes of our region.
My own interest in the genus has been fairly continuous over the past thirty years, slow at first and with a burst of interest in the 1990's when I began extensive inventory work in SW Oregon. Racomitrium in the broad sense is a key component of most exposed rock habitats, from streamside canyons to alpine ridges. It is not unusual to find several species growing on one rock. Some are common, some are rare. Learning to sort them out has been an engaging challenge. I have made two efforts to share what I have learned. The first was a booklet of illustrations of racomitriums (Wagner 1998) which summarized my understanding of the plants up to that time. (Note: what was labeled R. sudeticum in that booklet is actually R. occidentale.) In 2001 I began a digitized pictorial survey of Racomitrium s.l. which was never published. I have given electronic copies to participants in my bryophyte workshops. This guide is the next step in this effort. The goal has been to provide a guide that is both useful and takes advantage of digital formatting.
HOW TO USE THE KEY
This is a standard dichotomous key formatted for web site navigation. Each page in this key is a couplet with two contrasting leads. Decide which lead best fits the specimen being studied. The picture above the lead illustrates a primary character. Click on the moss green button at the left of the lead to go to the next couplet or to a species page. Each species page gives the pertinent synonyms, diagnostic characters and hints for differentiating look alikes, habitat and distribution, and comments.
All pictures on the key pages and the species pages are thumbnails, low resolution versions of the images which speed downloading. Click on a thumbnail to see a larger image. These higher resolution images may be be larger than your screen depending on your browser settings. They have been saved at 1000 pixels high to retain reasonably good resolution for printing. Use your back arrow, "Show the previous page," to return to the page on which the thumbnail was located.
All images used in the key are repeated on the appropriate species page. Most species pages have many additional photomicrographs.
At the top of every key page there is a line of breadcrumbs. This is a series of links to the leads in each couplet taken to arrive at this page. It is a shorthand record of choices made. You 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 take you back to the start of the key.
INDEX TO SPECIES
Go to Index of Species to find a list of all names with authorities covered in this guide. All names are linked to a species page, with the species pages listed under the same genera as found in FNA and the species names under Racomitrium listed as synonyms. There is a link to the index at the bottom of every key page. This permits a user to go directly to a species page to to see additional pictures of a species used to illustrate a lead. It may be possible to get a preliminary identification with a check to see if a specimen in hand fits the species recognition characters. One can follow up on this hint by using the breadcrumbs to go backwards through the key.
One of the incentives for creating a key with photomicrographs is to illustrate the variation in leaf surface ornamentation found in these plants. When present, the type of papillae is an important character widely used in distinguishing species of mosses. The papillae of racomitriums come in forms that are not common elsewhere among the mosses.
Elva Lawton (1971) writes, "There are a number of different kinds of papillae in Rhacomitrium as well as in other genera, and a thorough study, with clear definitions and perhaps names for different forms, is desirable. Sinuose cell walls complicate the problem because in some species the cells may appear papillose in surface view when no papillae are evident in section. Cross walls may be strongly thickened, bulging dorsally and ventrally, and in section may resemble papillae. In the keys, cells with bulging walls are not considered papillose."
In his monograph, Frisvoll (1988) called these bulging ends of transverse walls, "pseudopapillae." Ochyra and Bednarek-Ochyra also refer to these bulging cross walls as "pseudopapillae." On the other hand, they place great emphasis on recognizing the true papillae that characterize the genus Codriophorus. In her monograph, Bednarek-Ochyra (2006) writes, "The cells in the majority of Codriophorus species are distinctly papillose in a peculiar manner with large, flat papillae distributed on both the dorsal and ventral surfaces of the leaf over the longititudinal walls and major part of the lamina, leaving only a narrow split in the middle." This kind of papilla was noted by Lawton only in R. fasciculare while the other species of Copdriophorus she described in various ways, e.g., "with several small papillae per cell" in R. aciculare. Bednarek-Ochyra (2007) observes that this species actually has the large flat papillae characteristic of the genus Copdriophorus but in addition has small papillulae on top of the papillae!
The photomicrographs presented here should help elucidate what is being described in the literature. There are, indeed, species specific characteristics of leaf ornamentation but they elude precise verbal definitions. Among the racomitriums, the only papillae that everybody recognizes readily are those on the hairpoints of Racomitrium lanuginosum and leaf cells of Niphotrichum.
Although this key depends mainly on vegetative characters, the direction a seta twists is a very useful character in placing species in the correct genus. This is something that can be determined in the field with a 10X handlens. It is not easy at first but with a bit of practice the twist direction can be observed with 100% accuracy. Racomitrium lanuginosum as well as all species in the genus Niphotrichum have a right handed twist to their setae. Noting this will help confirm genus identification in the field as a supplementary character to the greyish white, hoary appearance of these plants.
All species of the other two segregate genera have a left handed twist to the dry seta except Bucklandiella lawtoniae. This will help sorting in the field whether a species similar to Bucklandiella heterosticha is at hand or a look alike in the genus Grimmia. It is not unusual for the less common species of Bucklandiella to hide among extensive patches of Grimmia trichophylla or G. leibergii, which have a right handed twist to their setae.
Note that some botanists, including Bednarek-Ochyra (1995) and Ochyra and Bednarek-Ochyra (2007), use a traditional but now deprecated terminology which is the opposite of contemporary scientific usage, e.g., using sinistrorse to describe a right handed twist and dextrorse for a left handed twist. Clear pictures demonstrating the correct usage can be found in the excellent illustrated glossary by Bill and Nancy Malcolm (2006, p. 110.).
Far more confusing is the use of clockwise and counterclockwise, without any qualifier, to describe the direction of twist. These terms describe a two dimensional trait while twist is a three dimensional character. A reference point plus direction of movement on a third axis must be specified in addition to clockwise/counterclockwise to define a twist. For example, all ordinary jars with screw top lids have a right handed twist to the threads. Looking down on the jar, twisting the lid clockwise will tighten it and turning counterclockwise will loosen it. However, if you hold the jar upside down, with the lid away from you, turning the lid clockwise will loosen the lid and counterclockwise will tighten it.
In the most widely accepted scientific terminology a right handed twist (best example: DNA) is defined as a helix inscribed by a point spiraling away from the viewer in a clockwise motion, such as a point on the lid of a jar as it is being tightened while you are looking down on it. A left handed twist is a helix inscribed by a point spiraling away in a counterclockwise motion. In more practical terms, based on looking at a vertically oriented seta from the side, right handed twists go up to the right and left handed twists go up to the left.
When Lawton (1971) uses clockwise, she is referring to a left handed twist and with counterclockwise she refers to a right handed twist. In only one place do Ochyra and Bednarek-Ochyra (2007) use clockwise: in describing the seta twist of Bucklandiella lawtoniae. This is the only species of this segregate genus with a right handed twist to the dry seta. Ironically, it is the only species in the genus Bucklandiella where the seta twist is mentioned in the species descriptions in the FNA. Because clockwise is used without qualifiers, it is not clear that these authors have noticed the distinctiveness of the seta twist in Bucklandiella lawtoniae, thus using the term in a manner opposite to Lawton's, or if they have simply overlooked it and equated clockwise with dextrorse (the term they use for left handed twist).
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My photomicrographs, as contained in this document, may be considered available for general use. Please do credit properly when used in other venues. Higher resolution versions are archived and available upon request. All the images are provided with specimen data and, if not specifically ascribed, all are in my personal herbarium. I hope others who do photomicrography of mosses will consider submitting their own images for me to incorporate into future editions of this key. With the racomitriums, one can never have enough pictures to look at. And I like the idea of this turning into a group project.
This document should receive regular revision and updating. Please do share with me any such edits or modifications you are willing to share.
It is my hope that the electronic format of this document will permit easy updating by anybody. By downloading this from disc or flash drive, anybody can modify the pages using a text editor or web writing program. With a downloaded version on a personal computer's hard drive one also has the advantage of being able to use the key without connecting to the internet. I will gladly mail out a CD with the most current version. Just send me a donation to cover copying and shipping. Send to the address on the home page.
I am indebted to several Bureau of Land Management botanists who have provided opportunities to explore and study the mosses of their districts. These include Nancy Wogen, Russ Holmes, Joan Seevers, Bruce Rittenhouse, Mark Mousseaux, and Ron Exeter. Also pertinent to this effort is the support of the U.S. Forest Service, in particular on the Winema Forest as coordinated by Sarah Malaby. Their encouragement to do field work and pass on what I have learned has been of inestimable value to me. I have received critical specimens to study from Ed Berg of the Kenai National Wildlife Refuge, Ron Exeter of Salem BLM, and Robin Lesher of the Mt. Baker-Snoqualmie National Forest. Dave Kofranek of Eugene has discovered and forwarded many interesting collections. Wilf Schofield and Judy Harpel assisted with reviews of identifications early in my work. For continuing advice and encouragement I am grateful to the gracious and generous communication from Ryszard Ochyra and Halina Bednarek-Ochyra; likewise Dan Norris and Jim Shevock have been very helpful in the field, lab, and in letters. The keys have benefited from review comments by Terry McIntosh and David Toren. I have been given space to work in the herbaria of Oregon State University and University of Washington; the latter has loaned me specimens. I am grateful to the curators of these institutions for these courtesies.
HOME GO TO KEY
Guide to Racomitrioideae of Oregon
Created 2007 Northwest Botanical Institute