EPOW - Ecology Picture of the Week

Thallus of the Lobaria

Lobaria linita, Family Lobariaceae
Umpqua River, Oregon USA

Explanation:  This lichen of western North America is characterized by a network of ridges on the upper surface of its thallus.  

Thallus?  A quick check of word origins suggests that the word thallus is Latin, in turn derived from the Greek thallos related to thalos meaning "scion, child" or offshoot.  A lichen thallus is that part of the growing structure that lacks true stems, leaves, or vascular tissue.  

This lichen species has been considered "at risk" with concern for its viability particularly in Oregon and California.  It is often found on mossy rocks in upper elevations, or along tree trunks in coastal humid forests.  It is sensitive to air quality and thus may serve as an indicator of pollutants.  

But, back to the thallus.  

Other members of the genus Lobaria (especially Lobaria pulmonaria) are known as "lungwort," as they were used in Europe by physicians to treat pneumonia and lung diseases because their thallus resembles lung tissue ... a case of the Doctrine of Signatures, a belief in centuries past that plants that resemble parts of the human body are useful medicinals for that part.  Apparently, however, this is unconfirmed by modern science.  

Information:
     McCune, B. and L. Geiser.  1997.  Macrolichens of the Pacific Northwest. Oregon State University Press, Corvallis, OR.