[Wikipedia] Description, Growth Rate: This lichen is fruticose, with very long stems and short, even side branches. It is considered the longest lichen in the world.[4] The stems are usually 15 to 30 cm in length but are sometimes much longer.[5] It is pale green to silvery-yellow. It has a distinct central cord, which is white.[6] D. longissima may grow to be 20 feet in length. It predominantly reproduces asexually through fragmentation. Spore-producing structures are rarely observed.[7] It can double its length each year. (link added by Mary Ann Machi)