Elongate Racomitrium Moss (Racomitrium elongatum)
Description
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.
Taxonomic tree
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Domain: Eukarya
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Kingdom: Plantae
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Phylum: Bryophyta
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Class: Bryopsida
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Order: Grimmiales
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Family: Grimmiaceae
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Genus: Racomitrium
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