Racomitrium varium (Mitt.) Jaeg.


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Synonym: Codriophorus varius (Mitt.) Bednarek-Ochyra & Ochyra; Frisvollia varia (Mitt.) Sawicki, Szczecńska, Bednarek-Ochyra & Ochyra

Special status: NONE

Recognition: Field identification of Racomitrium varium is reasonable only with the typical form that has well developed hair points on its leaves. This common, pilose form is the only one found on upland sites; the rare form with muticous leaves so far is confined to rocks close to streams. However, even in riparian zones the pilose form is the most frequently encountered.

The pilose form can be recognized by repeating (annual) shoot sectors with both muticous leaves and pilose leaves. The muticous leaves are produced early in the season and pilose leaves later in the growing season. Although all the species with hair points have a few leaves that lack hair points, these are much smaller than ordinary leaves and clearly poorly developed. The muticous leaves of Racomitrium varium are well developed and simply precede the pilose leaves. Learning to recognize the species in the field takes some experience but in time it can be done using a hand lens with a high level of confidence. Part of the problem is that the general aspect of the plants vary more than other racomitriums. It typically occurs in thick mats with relatively unbranched shoots. When this species is invades fresh rock surfaces it sends out long shoots with short, curved side branches that mimic the branching patterns more typical of subgenus Niphotrichum.

The strictly muticous form, of a type called an "epilose ecad" by Frisvoll, is not distinguishable in the field from other muticous species, as in subgenus Cataractae (= genus Codriophorus) or Racomitrium pacificum. When muticous species of racomitriums are found and no teeth are observed at the apex, collections must be taken back to the laboratory for microscope examination in order to establish a confident identification. Among these collections will likely be Grimmia ramondii (= Dryptodon patens), distinguished by high wings on the dorsal costa. These wings may be discerned in the field with a 20X hand lens, good light, and adequate experience. When fertile, the right handed twist characteristic of Grimmia will confirm this determination.

The alar region provides a critical character for confirming identification. This species has, on most leaves, a long row of elongate, thin walled cells from the leaf insertion up the margin for 15 or 20 cells. Pellucid is the term used to described these cells which are much paler than cells with thick, sinuose nodose walls. Frequently there is a second row of pellucid cells interior to the margin. It is important to note that it is not unusual for the margin to be poorly developed on one side of the leaf. This seems to be most prevalent on shoots where the leaves are inserted at a slight angle, so that the margin is best developed on the lower edge and less developed on the upper edge that is closest to the shoot tip.

Because Racomitrium varium occurs in two forms, and the presence of hair points is a critical character in the keys, the species appears twice in the key. In each case, it is contrasted with a species which has a margin of pellucid cells that extend above the alar region to the supra alar region. The pilose form is distinguished from Racomitrium microcarpon by basal cells, relatively thin walled in Racomitrium varium, and leaf ornamentation. The leaf cells in Racomitrium varium have flat papillae over the vertical walls while the cells have pseudopapillae over the vertical walls in Racomitrium microcarpon.

The nearest look alike to the muticous form of Racomitrium varium is Racomitrium fasciculare, the only other species of subgenus Cataractae that has a long, pellucid basal margin. The differentiation here depends on leaf cross sections: Racomitrium varium has a thicker costa, typically 3 cells thick above midleaf, channeled above, and in Racomitrium fasciculare the costa is only 2 cells thick above base, almost flat. Note that Racomitrium fasciculare has been reported from Oregon only once (Ochyra and Bednarek-Ochyra 2007), so that even though the muticous form of Racomitrium varium is rare, it is still more likely to be encountered than Racomitrium fasciculare.

Distribution: On rocks in varied habitats, from the splash zone of streams to upland sites in full sun. It is an able pioneer and covers rocky road cuts in shady sites. Because of the ecological tolerance, this is the most widespread, common species of the genus Racomitrium. It is more abundant at lower and middle elevations than at high elevations.

Comments: An interesting character of this species is that it has the longest peristome of any in the genus (1.0-2.0 mm). Although not highly useful as a general field identification character, it presents a beautiful and dramatic appearance under the hand lens in spring when the capsules are ripe and the opercula have just fallen. Unfortunately, the peristome teeth are extremely fragile and are lost within a very few weeks even though the capsules themselves persist for over a year. This is one of the reasons the peristome teeth are not as useful as they might be for identification.

The phylogenetic placement of this species has gone through major convolutions. It was placed in the genus Codriophorus in 2003 and more recently placed in a separate, monotypic genus, Frisvollia (Sawicki, Szczecńska, Bednarek-Ochyra & Ochyra, 2015) to deal with its anomalous characters. My opinion remains unchanged, that retaining Racomitrium in its broad, inclusive sense is best.


Racomitrium varium; Ferris Gulch, Jackson Co., Oregon. DHW 9285.



Racomitrium varium; Keeler Creek, Jackson Co., Oregon. DHW m0065.



Racomitrium varium; Keeler Creek, Jackson Co., Oregon. DHW m0065.



Canton Creek Reserve, Douglas Co., Oregon. Figura s.m. 1998.



Racomitrium varium; Canton Creek Reserve, Douglas Co., Oregon. Figura s.m. 1998.



Racomitrium varium; Canton Creek Reserve, Douglas Co., Oregon. Figura s.m. 1998.



Racomitrium varium; Canton Creek Reserve, Douglas Co., Oregon. Figura s.m. 1998. Note: the groove in the back of the costa is not typical for this species. The 3-stratose costa is typical, as is the blocky shape.



Racomitrium varium; Canton Creek Reserve, Douglas Co., Oregon. Figura s.m. 1998.



Memaloose Park, Wasco Co., Oregon. D. Wagner m0817g.



Racomitrium varium; Memaloose Park, Wasco Co., Oregon. D. Wagner m0817g.



Memaloose Park, Wasco Co., Oregon. D. Wagner m0817g.



Racomitrium varium; Memaloose Park, Wasco Co., Oregon. D. Wagner m0817g.



Racomitrium varium; Memaloose Park, Wasco Co., Oregon. D. Wagner m0817g.



Racomitrium varium; Memaloose Park, Wasco Co., Oregon. D. Wagner m0817g.



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Guide to Racomitrium of Oregon
Created 2007 Northwest Botanical Institute