Today's image is courtesy of Dr. Robin Young, who is presently a Post Doctoral Fellow in the BioImaging Facility here at the University of British Columbia. Robin was previously a graduate student with Dr. Lacey Samuels. Thank you, Robin!

It is likely that some BPotD readers will already have encountered this image elsewhere, as it was the 4th place winner in the 2011 Nikon Small World Photomicrography Competition. Robin also received an Image of Distinction award with this photomicrograph of a Lunularia cruciata gemma, or asexual reproductive organ (BPotD entry on Lunularia cruciata). I spotted a feature article on these photomicrographs a few days ago on the CBC web site: "Microscopic marvels showcased". This image is taken at 20x magnification, and utilizes intrinsic fluorescence.

Although it is difficult to pull together distribution information for liverworts, it seems that Lepidozia reptans, or little hands liverwort, is widespread in the northern hemisphere (I've found references for China, much of North America including the southeast and northwest, and northern Europe) and disjunct in South America. It is certainly common locally, and I often spot it on decaying or slow-growing branches in moist, shady sites. A few additional photographs of this liverwort are available from UBC's Biology 321 (Bryophytes) class web site: Lepidozia reptans.

Lastly, on the subject of contests, readers who are photographers of the regional flora of the Pacific Northwest of North America may be interested in this Botanical Art Exhibit and Contest. It is to be held in conjunction with the Conserving Plant Biodiversity in a Changing World Conference in March. Full instructions are available via the link; subject matter "reflects the beauty of flora throughout northwestern North America" and "It is essential that the subject matter is native to the northwestern North America (Yukon, British Columbia, Alberta, Alaska, WA, OR, ID, and MT)". There's no huge financial incentive to participate (in fact, it will likely cost a small amount due to the need for artists being responsible for framing and shipping expenses), but it's certainly a good way to draw attention to the issues being discussed.

Thank you to BlueRidgeKitties@Flickr for sharing these two photos (photo 1 | photo 2) via the Flickr Pool. These images of Bazzania trilobata were made near Linville Falls in North Carolina.

Liverworts can be broadly separated into two distinct artificial groups: leafy and thalloid. Bazzania trilobata is an example of a leafy liverwort. Though they look like mosses and have a similar life cycle, leafy liverworts have important morphological differences that set them apart. For example, liverwort leaves are often in two lateral ranks with a third row of smaller leaves on the back of the stem, while moss leaves have a spiral arrangement (Vitt et al's Mosses, Lichens & Ferns of Northwest North America (1988)).

Bazzania trilobata grows in "large clumps or dense widespread mats on boggy soils, forest ground, rotten logs, and at the bases of trees especially in cedar swamps and hemlock or boreal forests". It is difficult to track down a precise distribution for the species, but it has been observed in northern temperate forests at a minimum. Generally, Bazzania species are more typical of tropical environments, though they grow in a wide range of climatic conditions, only excluding deserts and the poles (Schofield's Field Guide to Liverwort Genera of Pacific Northwest America (2002)).

The leaf orientation of Bazzania trilobata is worth noting, as it is the opposite of most liverworts. As seen in the close-up photo, the upper edges of this species' leaves overlap the lower edges of the leaves above them. This is described as an incubous leaf arrangement. The majority of leafy liverworts have the opposite arrangement, succubous, where the lower edges of the leaves overlap the upper edges of the leaves below them.

Crescent-cup liverwort has a cosmopolitan (worldwide) distribution. However, I've found it difficult to determine its native distribution using online resources. At the least, it is apparently native to western Europe, but not native to either of New Zealand or Ontario. I'm certain there are other places where it has been introduced, though – it is a common greenhouse weed. It is easy to imagine how this liverwort could be introduced to much of the world through the exchange of plants.

The small, yellowish-green bodies held within the crescent-shaped cups are gemmae, vegetative propagules of the parent plant that are produced asexually (i.e., they are genetically identical to the parent). Raindrops falling into the cups splash outwards, expelling the gemmae out of the cup. If fortune holds (what if your future depended on a raindrop?), the gemma would be transported to a suitable site and grow into a genetically identical clone of its parent plant.

Photography resource link: Images of southwestern Australia from photographer Alex Bond. Click on “Limited Edition Collection” to view his two galleries of photographs – and yes, there are kangaroos.

I'm on vacation, so only a short written accompaniment today. – Daniel

Porella cordaeana is a liverwort (and the first liverwort entry on Botany Photo of the Day). Liverworts are divided morphologically into two main groups: the leafy liverworts which appear similar to mosses (such as Porella) and the thalloid liverworts. To see the difference in structure, visit An Introduction to Liverwort Morphology via the web site of UBC's bryophytes course.