University of Washington Seattle Campus, Washington: May 21, 2012

Location: Burke-Gilman Trail near Botany Greenhouse, University of Washington Seattle Campus, Seattle, Washington, 98105, USA

Date: May 21, 2012

Time: 12:00 PM – 3:20 PM

Summary of Observations: Today I spent a few hours looking at different samples of mosses under the dissecting microscope at the UW Botany Greenhouse. I collected my samples from the Burke-Gilman bridge just adjacent to the Botany Greenhouse. I am still by no means an expert on mosses, but after examining these samples, I believe I was looking at: (1) Red Roof Moss, (2) Lyell’s Bristle Moss, (3) Black-Tufted Rock Moss and (4) a species in the Genus Plagiomium.
Looking at a few different field guides, I learned that when trying to ID a moss, you should consider: (1) Is it a liverwort, lichen, or moss? The best way to tell these apart is by the presence of capsules. In mosses, the capsule enlargement/maturity takes place after seta elongation (so, capsule develops after stem grows up). Further, the capsule usually has one end to let spores out. In liverworts, capsule matures and splits into segments, then the seta elongates. However, capsules are only present in both groups during the spring. So, you can also look under a microscope: the leaves of all these groups look very different.
I also learned a few different tools to figure out what species of moss your specimen is, once you have determined that it is indeed a moss. You should consider: (1) Where it is growing: recognizing if it is growing on a rocky substrate, and if so, if the substrate is acidic or basic, or an organic substrate like tree or soil, and if so, if it is growing on a coniferous or deciduous tree. Acidic rocks are igneous rocks that have a relatively high silica content (like granite and rhyolite). Basic rocks have low silica content, like basalt. These are important to understand because different mosses prefer different substrates. (2) The presence/characteristics of the sporophyte, which often has a distinguishing shape and/or color. (3) The structure of the actual plant: is it branched or un-branched? Occurring in clumps or as single stems mixed in with other mosses? (4) Finally, the best way is to look at the species under a microscope. Here, you should examine the leaves (especially look at leaf shape) and sporophyte (the shape can be difficult to discern without a microscope). A good tip I learned was to put the moss under hot water first, causing it to expand and loosen its leaves.
I used all of these tips to determine which species I was looking at today. I expected one sample was the Red Roof Moss because I found it all over the bridge, and this moss commonly grows in a variety of usually inhospitable habitats (like sidewalks). Further, it had the distinctive coloring of the Red Roof Moss. However, I wasn’t completely confident that I was looking at Red Roof Moss until I examined the sporophyte under the dissecting microscope, and recognized the distinctive shape of its capsule. I identified another species as Lyell’s Bristle Moss by its distinctive shape and brown-green color gradient, but also by its irregularly branched growing pattern. The third sample I identified as Black-Tufted Rock Moss because it was dark, almost black on the bottom and brighter green on the top and was un-branched. Also, because this species likes periodically wet rocks. The last sample I identified down to the genus Plagiomium because of the growth pattern of the leaves: looking straight down onto the sample, looked like a flower. Also looked at the shape of the leaves: it had wide, egg-shaped leaves.

Comments/Questions: I learned that the leaves of a moss are only one cell thick, making them pretty cool to look at under a microscope.

Species List

1. Ceratodon purpureus (Red Roof Moss)
2. Orthotrichum lyellii (Lyell’s Bristle Moss)
3. Racomitrium aciculare (Black-Tufted Rock Moss)
4. Genus Plagiomium

Posted on June 4, 2012 08:08 PM by sophiejhart