Racomitrium elongatum Ehrh. ex Frisv.
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Synonym: Niphotrichum elongatum (Ehrh. ex Frisv.) Bednarek-Ochyra & Ochyra
Special status: NONE
Recognition: The long, white hairpoints and prominent papillae on the leaf cells are unmistakable features of the subgenus Niphotrichum, giving them an appearance that one can learn to recognize at 50 paces. However, distinguishing this species from the other two subgen. Niphotrichum species found in Oregon is truly challenging. Until recently, all three local species of the genus were lumped under a single species name, which we called Racomitrium canescens. Most past records of this species from the region are most likely to be R. elongatum. The other species of Niphotrichum are so much less common that one should rule out this species before naming a specimen as R. canescens or R. ericoides. This separation cannot be done without using a compound microscope to examine leaves on a slide. Fortunately, leaf section preparations are not necessary because no additional taxonomically useful data can be so obtained (as far as currently known). The contemporary keys separate R. canescens on the basis of its costa being relatively distinctive compared to R. elongatum/ericoides. Both Racomitrium elongatum and Racomitrium ericoides have a slender costa that terminates just below the hair point, the costa sitting in a narrow channel. Racomitrium canescens, on the other hand, has a shortish, irregular costa, often slightly branched, that terminates well below the hair point in a broad trough at the leaf apex.
But if that seems subtle, separating R. ericoides from R. elongatum approaches the incredible. Here, one needs to guage the less bumpy hair points and longer pellucid border on basal leaf margins on the more rare R. ericoides. Reliable identification is not going to be done with confidence strictly by using these (or any other) keys for the first time. These keys work as well as any but appreciating the difference in development of supra alar marginal cells, the most consistent qualitative character, comes only from having studied many leaves from many specimens. What comes to mind is a phrase in one of R.M. Schuster's volumes on liverworts. He was able to describe a particular specimen confidently only "...after several hours of protracted study." This is as good a place as any to remind students that mastering moss identification takes a generous amount of time devoted to careful study. Without this kind of effort, separating species of Racomitrium is at best an "educated guess."
Distribution: On rock and sand (remembering that sand is merely finely dispersed rock); from the coast to high in the mountains. This is an extremely common species in western Oregon, a contender with Racomitrium varium for most abundant of the racomitriums. The most extensive populations are to be seen on sand along Highway 101. Otherwise, the species seems to prefer slightly drier surfaces than Racomitrium varium.
Comments: One other species that could be confused with species of subgenus Niphotrichum is Racomitrium lanuginosum; it is not a big problem for us because so rare in Oregon. It does have a hoary appearance from a distance because of its long, hyaline hair points. The distinctive dentate hair points of Racomitrium lanuginosum are easily seen with a 10X hand lens.
Racomitrium elongatum - Irwin Rocks, Douglas Co., Oregon. DHW 7868a.
Racomitrium elongatum - Wolf Creek, Lane Co., Oregon. DHW 7384.
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Guide to Racomitrium of Oregon
Created 2007 Northwest Botanical Institute