Racomitrium affine (Schleich. ex Web. & Mohr) Lindb.


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Synonym: Bucklandiella affinis (Schleich. ex Web. & Mohr) Bednarek-Ochyra & Ochyra

Special status: NONE

Recognition: In the field this is slightly darker than Racomitrium heterostichum but otherwise very similar: a medium size racomitrium with fairly long hairpoints. The leaf margins are mostly unistratose like Racomitrium heterostichum, but differs from that in its rather thick, nearly terete costa, mostly 3 stratose at midleaf and 3-4 stratose towards leaf base. From Racomitrium lawtoniae it is distinguished by the size but similar in having a slender hairpoint which is more or less decurrent. Racomitrium lawtoniae has a right handed twist to its seta while Racomitrium affine has the left handed twist typical of the rest of genus. In the field Racomitrium affine could be confused with Grimmia trichophylla or Grimmia leibergii except for the twist of the seta (right handed in Grimmia) and the sinuose nodose basal cells of the leaves (sinuose only in cells of distal part of leaf in Grimmia.)

Distribution: Not common but apparently widespread in Oregon.

Comments: This species sometimes has bistratose margins in one cell row on some leaves and is reported to have forms with no or very short hairpoints. The few plants I have identified all have long hair points. This species sometimes has bistratose margins in one cell row on some leaves. The occasional sections with a bistratose margin are scarce but they do occur regularly (Bednarek-Ochyra 1995). This is important to remember if one encounters such a section: it doesn't rule out R. affine. This situation emphasizes the importance of making preparations with many sections from more than one shoot.

Note that occasionally a leaf section will exhibit abaxial indentations in the costa, as in the fourth photo below. This could be confused with the situation in Racomitrium occidentale, where abaxial grooves are characteristic. However, almost all leaf sections of R. affine lack grooves in the distal half of the leaf, where grooves are most prominent in R. occidentale. This demonstrates that anatomical characters are always variable to a certain degree and further emphasizes that more than one section should be observed before conclusions are drawn about the nature of a character trait for a particular specimen.


Mt. Isabelle, Jackson Co., Oregon. DHW m0474. NOTE: THUMBNAILS SHOW ONLY A PORTION OF THE LARGER IMAGE.



Mt. Isabelle, Jackson Co., Oregon. DHW m0474.



Mt. Isabelle, Jackson Co., Oregon. DHW m0474.



Mt. Isabelle, Jackson Co., Oregon. DHW m0474.



Irwin Rocks, Douglas Co., Oregon. DHW 7869.



Irwin Rocks, Douglas Co., Oregon. DHW 7869.



Irwin Rocks, Douglas Co., Oregon. DHW 7869.



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Guide to Racomitrium of Oregon
Created 2007 Northwest Botanical Institute