Muehlenbeck’s thread-moss was formerly part of a large and difficult-to-identify group of mosses in the genus Bryum . Based on recent changes in the Flora of North America, this group has been split into several smaller groups and Muehlenbeck’s thread-moss which used to be Bryum muehlenbeckii is now known as Imbribryum muehlenbeckii. The new genus name that begins with “imbri” comes from the word “imbricate” which is a technical term that refers to the closely overlapping leaves like shingles on a roof that characterize the species that now belong to this genus. (Speaking of names, almost any species name that ends in “ii” are species that are named after someone – in this case – Henri Gustave Muehlenbeck, an Alsatian physician and botanical collector).
On a recent hike near Opax Mountain, we came across an unusual type of ecosystem that I don’t often see. It was a part of a long rock ridge with very shallow soils and lots of exposed bedrock. What was unusual was that portions of the rocky slopes had wet areas where water seeps across the shallow rocky surfaces. These sites are always interesting to explore because they are often home to a number of rare or uncommon plants. Many of the seeps had naked broomrape, a parasitic plant lacking chlorophyll that lives off the roots of other plants. I have not seen this species in the Kamloops area before.
On some of the seepy areas growing directly on bedrock was a reddish green shiny moss which I initially thought was red thread-moss (Imbribryum miniatum) a species I’ve seen on similar sites on the coast but had never seen in the BC Interior. The following two photos are red thread-moss from rock outcrops on Vancouver Island. Plants vary from bright glossy green to red.
However, after working my way through the keys, it looks like the species I saw is really Muehlenbeck’s thread-moss. This moss is very similar and I have only seen it a few times before but it also occurs on seepy rocky sites. The two species are very similar but the leaves of red thread-moss are generally more overlapping giving the stems a “julaceous” appearance (a technical term for “wormy”) and the leaves tend to be more rounded at the tips. The following photo is Muehlenbeck’s thread-moss collected from Opax. Although some of the leaves have rounded tips, many are sharp and pointy.
I’ve always liked the leaf cells of most thread-moss species – they look like pieces of beveled glass in a stained-glass window. The cells near the leaf tip tend to have a narrow-diamond shape whereas those near the base of the leaf are short and square.
It’s interesting how two species that are very similar in appearance also occupy very similar habitats.