On a recent hike to Wells Gray Park, we hike along the edge of a volcanic plateau that overlooks the Clearwater River.

All along the trail were stands of birch, aspen, lodgepole pine, Douglas-fir, western redcedar, and the odd western hemlock.

At one point, I was trying not to trip over an aspen trunk that was lying across the path when I noticed a small cushion-like moss on the hard, smooth bark.

I don’t usually look at birch or aspen for mosses as their bark is not a very hospitable place for many species so I was intrigued by this small moss that had been growing on the trunk for some time. It didn’t look like any moss that I was familiar with so I grabbed a little bit to take home with me.

When I first looked at it under the dissecting scope, the moss was dry and the individual stems had tightly overlapping leaves.

When I added a few drops of water, the plants almost go through an instant transformation with the leaves unfurling outwards – almost like an act of magic.

When I examine the individual leaves under the compound microscope, they are quite distinctive. They are concave with broadly rounded leaf tips. I knew it was probably a type of moss belonging to the genus Orhtotrichum of which there are about 20 species in BC and are often difficult to identify so I didn’t hold out too much hope.

Like most mosses, the leaves are only one-cell thick. The leaf cells of this moss are quite attractive and form nice orderly rows of round cells with very thick cell walls. Each cell has a large bump over the center of the cell. These are quite common in some mosses and are a useful character in their identification.

Here you can see the individual bumps (called papillae) when the leaf is viewed along the margin.

The other distinctive feature of this moss, is that the leaves have scattered brown bumps on the surface. These are gemmae, specialized asexual reproductive bodies that can fall off and grow into a new moss.

The presence of gemmae and the rounded leaf tips made it possible for me to identify this species as Orthotrichum obtusifolium or blunt-leaved bristle-moss. It seems to be quite a common and distinctive species but one that I had not come across before. I found the leaves and the arrangement of leaf cells to be very attractive under the microscope so I’ll have to look for this moss on aspen and see if it is also a common species around Kamloops.