Ramalina Farinacea

Day 192: Lichens have been around for a long time. Obviously, they were preceded by algae, fungi and yeasts because all three are components of the structures we now call lichens, but they were already well established when herbivorous dinosaurs went looking for snacks. Many lichens reproduce both sexually and asexually, a factor which gives them a distinct leg up as to their survival capabilities. Sexual reproduction draws genetic material from two sources, mingling DNA to form new individuals. Asexual reproduction clones the parent material, i.e., the DNA of the new lichen is the same as that of the original. Ramalina farinacea rarely develops apothecia, the fruiting bodies which contain the spores necessary to sexual reproduction, but the margins of its lobes are often heavily populated with elliptical soralia containing hundreds of soredia, its vegetative clones. The soralia are quite obvious in the photo of a fresh specimen on the left. Can you spot them, still holding thousands of green and viable soredia, on the dried-up specimen on the right? Although the parent body is dead, it has the potential to live on in copies of itself. Barring a mass extinction of all life on the planet, I'm betting lichens will be around long after H. sap. has died off.

Hypogymnia Physodes

Day 168: Collectively, the Hypogymnias are commonly known as "tube lichens." Why? If you examine one closely, you will see that the lobes are puffy, like miniature balloon animals. In some species, this resemblance is accentuated by each lobe being pinched at the base. Hypogymnia physodes does not exhibit these restrictions, but it has another characteristic which makes it relatively easy to identify, and one which gives it its common name of "Monk's-hood Lichen." The inset takes a closer view of the lobe tips, revealing the powdery or granular soralia (asexual reproductive structures) typical of this species. Where the soralia have fallen away, the tubular nature of the lobes becomes obvious. The lower surface of this lichen is black, but if it is separated from the upper layer to reveal the underside of the pale green top (the medullary ceiling), it will be seen to be white. Differences in the colour of the medullary ceiling are also diagnostic when trying to identify Hypogymnias.

Ramalina Farinacea, Sorediate Margins

Day 76: Lichen terminology can be very confusing even for botanists because certain structures have no counterpart in the physiology of vascular plants. My readers will have heard me use the term "soredia/soredium" for a specific type of vegetative propagule generated by some lichens, and they may also recall having read the word "soralia." Soralia are where soredia are produced. They manifest as small patches where the lichen cortex ("skin") has cracked or broken down. The emerging soredia often have a granular appearance and lack any cortex; soredia are one of the parent lichen's means of reproducing. In the inset, you can see the soralia/soredia along the margins of this fine specimen of Ramalina farinacea from Ohop Valley. Many lichens have more than one reproductive strategy to ensure their survival as species. Some are capable of reproducing both sexually and asexually. On the whole, lichens are atonishingly successful in the natural scheme. They were here long before humankind, and unless we pollute them out of existence, they will endure long after evidence of our brief passage has faded from the surface of the Earth.