Racomitrium lawtoniae Ireland


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Synonym: Bucklandiella lawtoniae (Ireland) Bednarek-Ochyra & Ochyra

Special status: NONE

Recognition: The large leaves (>4 mm) with strong, decurrent awns are the distinctive features of this species. Because the leaf margins are hardly recurved, it is possible to be satisfied that leaf margins are unistratose without sectioning the leaves. The decurrent awns are supposed to be so distinctive that it is not necessary to section leaves to make a confident identification. However, R. affine may also have hyaline decurrencies which are equally distinctive, but the leaves are always much smaller than 4 mm. The costa section is not instructive: both have rather blocky cross sections. The awns are the best distinguishing microscopic feature: quite spinulose in R. affine and barely serrulate in R. lawtoniae. Fertile specimens are instantly recognized by the twist of the seta that is opposite to all others species of subgenus Ellepticodryptodon (=Bucklandiella): right handed instead of left handed.

Distribution: On rocks; frequent from Washington to Alaska. Not yet known from Oregon but reported from Siskiyou County, California (Norris & Shevock 2004a) so to be expected to turn up somewhere in the Oregon Cascades.

Comments: The right handed twist to the seta of R. lawtoniae has proven to be quite consistent. It has been observed in all fertile specimens. It is important to remember that Bednarek-Ochyra uses the term "sinistrorse" for right handed and "dextrorse" for left handed twists. This unfortunate misuse of terms is likely to cause confusion for some time to come.


Racomitrium lawtoniae; Mt. Pilchuck, Snohomish Co., Washington. R. Ireland 6116.



Racomitrium lawtoniae; Mt. Pilchuck, Snohomish Co., Washington. R. Ireland 6116.



Racomitrium lawtoniae; Mt. Pilchuck, Snohomish Co., Washington. R. Ireland 6116.



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Guide to Racomitrium of Oregon
Created 2007 Northwest Botanical Institute