of the thallus that can be revealed by gently pulling a filament apart from either end. It reproduces via vegetative means through fragmentation, asexual means through soredia, or sexual means through ascogonium and spermatogonium. The growth rate of lichens in nature is slow, but the growth rate has been sped up in laboratory conditions where Usnea is being cultured. Usnea looks very similar to the plant Spanish moss, so much so that the latter's Latin name is derived from it (Tillandsia usneoides, the 'Usnea-like Tillandsia'). Ecology Like other lichens, Usnea often grows on sick or dying trees due to the pre-existing loss of canopy leaves, allowing for greater photosynthesis by the lichen's algae; this leads some gardeners to mistakenly blame the lichen for the tree's leaf loss and illness. Usnea is very sensitive to air pollution, especially sulfur dioxide. Under poor growing conditions, such as areas high in pollution, they may grow no larger than a few millimetres, if they survive at all. Where the air is unpolluted, they can grow to 10–20 cm long. It can sometimes be used as a bioindicator, because it tends to only grow in those regions where the air is clean, and of high quality. Uses Medical claims According to Paul Bergner, Author of Medical Herbalism. "The usnic acid in Usnea is effective against gram positive bacteria such as Streptococcus and Staphylococcus, making Usnea a valuable addition to herbal formulas for sore throats and skin infections. It is also effective against a bacterium that commonly causes pneumonia" There is reason to believe that Usnea, in high concentrations, could possess some toxicity. The National Toxicology Program is currently evaluating the issue. Dyes Usnea species have been used to create orange, yellow, green, blue, and purple dyes for textiles. Cosmetics Usnea barbata has been used in cosmetic production for its antimicrobial and antifungal properties as a preservative and deodorant. Combustible Usnea barbata when dry is extremely flammable and is often used as a firestarter. Species Usnea acromelana Usnea alboverrucata Usnea amblyoclada Usnea angulata Usnea antarctica Usnea aranea Usnea articulata Usnea aurantiaciparvula Usnea austrocampestris – Falkland Islands Usnea bismolliuscula Usnea boomiana Usnea brattiae Usnea cavernosa Usnea cedrosiana Usnea ceratina Usnea chaetophora Usnea cirrosa Usnea clerciana Usnea confusa Usnea cornuta Usnea crenulata Usnea crocata Usnea cylindrica Usnea diplotypus Usnea effusa Usnea elata Usnea elixii Usnea esperantiana Usnea exigua Usnea filipendula Usnea firmula Usnea flammea Usnea flavocardia Usnea flavorubescens