Description
The vegetative body of the lichen, the thallus, is foliose, and typically less than 8 centimetres (3.1 in) wide. The lobes of the thallus are 1–4 mm in diameter, and flattened down. The upper surface is some shade of yellow, orange, or greenish yellow, while the lower surface is white, with a cortex, and with sparse pale rhizines or hapters. The vegetative reproductive structures soredia and isidia are absent in this species, however, apothecia are usually present.
The outer "skin" of the lichen, the cortex, is composed of closely packed fungal hyphae and serves to protect the thallus from water loss due to evaporation as well as harmful effects of high levels of irradiation. In Xanthoria parietina, the thickness of the thalli is known to vary depending on the habitat is which it grows. Thalli are much thinner in shady locations than in those exposed to full sunshine; this has the effect of protecting the algae that cannot tolerate high light intensities. The lichen pigment parietin gives this species a deep yellow or orange-red color.
X. parietina prefers growing on bark and wood; it is found more rarely on rock. Nutrient enrichment by bird droppings enhances the ability of X. parietinato grow on rock.
Read more about this topic: Xanthoria Parietina
Famous quotes containing the word description:
“To give an accurate description of what has never occurred is not merely the proper occupation of the historian, but the inalienable privilege of any man of parts and culture.”
—Oscar Wilde (1854–1900)
“I was here first introduced to Joe.... He was a good-looking Indian, twenty-four years old, apparently of unmixed blood, short and stout, with a broad face and reddish complexion, and eyes, methinks, narrower and more turned up at the outer corners than ours, answering to the description of his race. Besides his underclothing, he wore a red flannel shirt, woolen pants, and a black Kossuth hat, the ordinary dress of the lumberman, and, to a considerable extent, of the Penobscot Indian.”
—Henry David Thoreau (1817–1862)
“The type of fig leaf which each culture employs to cover its social taboos offers a twofold description of its morality. It reveals that certain unacknowledged behavior exists and it suggests the form that such behavior takes.”
—Freda Adler (b. 1934)