page_title: Hypogymnia
section_title: Description
hierarchical_section_title: Hypogymnia / Description
caption_attribution_description: Hypogymnia occidentalis 20090521.23 Wells Gray Provincial Park, BC
context_page_description: Hypogymnia is a genus of foliose lichens in the family Parmeliaceae. They are commonly known as tube lichens, bone lichens, or pillow lichens. Most species lack rhizines that are otherwise common in members of the Parmeliaceae, and have swollen lobes that are usually hollow. The lichens usually grow on the bark and wood of coniferous trees.
  Hypogymnia was created by botanist William Nylander, first as a subgenus of Parmelia in 1881, and 15 years later as a distinct genus of two species, including the widespread and common type species, Hypogymnia physodes. It has since grown to about 90 recognized species. Hypogymnia has a centre of biodiversity in China, where many of its species are found.
context_section_description: Hypogymnia is a genus of medium to large foliose lichens. They are typically greenish grey to brownish grey in colour; some species are yellowish (from usnic acid). The thallus comprises more or less inflated but hollow (tube-like) lobes. These lobes often have a perforation at the tip. The colour of the ceiling of the tubes (the medullary surface) is dark brown or white, and is often used as a characteristic to distinguish between species. The lower surface of the tube is black with a smooth or wrinkled texture.
  Rhizines  are root-like attachment organs on the lower surface of a lichen thallus, made of elongated strands of hyphae; a shorter version of this attachment organ is called a hapter. Although many recent lichen floras and manuals describe Hypogymnia as lacking rhizines, a 2015 study challenges the universality of this assertion. In the study, researchers studied a large number of Hypogymnia collections, representing 72 species as well as 64 type specimens. They found that rhizines and hapters were occasionally present on the lower surface of 35 species. Two types of attachment organs are found: slender rhizines with fine and tapering tips (found in H. krogiae and H. subfarinacea), and the more common hapters, which are thick with broken tips. Both types are dark brown to black and usually the same colour as the lower surface. In all cases where these attachment organs are found, however, they are few in number and are sparsely distributed on the lower thallus surface.
  The apothecia of Hypogymnia are lecanorine in form with a constricted base and are often raised or shaped like an urn. The apothecial discs are red-brown and typically concave. Ascospores are colourless, ellipsoid, and number eight per ascus. They are relatively small, less than 9 μm long. Pycnidia are black and appear as small dots on the surface of the lobes. The cortex contains atranorin (responsible for the grey colour), while the medullae of most species have physodic acid, and some species contain other orcinol and beta-orcinol depsidones, including protocetraric acid and physodalic acid.
  The genus Menegazzia contains species that could be confused with Hypogymnia; Menegazzia, however, has perforations on the upper lobe surface, unlike Hypogymnia. Other superficially similar genera, such as Brodoa and Allantoparmelia, can be distinguished from Hypogymnia by their solid lobes.
caption: Closeup of a perforated lobe tip of H. occidentalis
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