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 poison oak /-ˈok/ 名詞
 槲葉毒葛

 Oak n.
 1. Bot. Any tree or shrub of the genus Quercus.  The oaks have alternate leaves, often variously lobed, and staminate flowers in catkins.  The fruit is a smooth nut, called an acorn, which is more or less inclosed in a scaly involucre called the cup or cupule.  There are now recognized about three hundred species, of which nearly fifty occur in the United States, the rest in Europe, Asia, and the other parts of North America, a very few barely reaching the northern parts of South America and Africa. Many of the oaks form forest trees of grand proportions and live many centuries. The wood is usually hard and tough, and provided with conspicuous medullary rays, forming the silver grain.
 2. The strong wood or timber of the oak.
 Note: ☞ Among the true oaks in America are: Barren oak, or Black-jack, Quercus nigra.
 Basket oak, Quercus Michauxii.
 Black oak, Quercus tinctoria; -- called also yellow oak or quercitron oak.
 Bur oak (see under Bur.), Quercus macrocarpa; -- called also over-cup or mossy-cup oak.
 Chestnut oak, Quercus Prinus and Quercus densiflora.
 Chinquapin oak (see under Chinquapin), Quercus prinoides.
 Coast live oak, Quercus agrifolia, of California; -- also called enceno.
 Live oak (see under Live), Quercus virens, the best of all for shipbuilding; also, Quercus Chrysolepis, of California.
 Pin oak. Same as Swamp oak.
 Post oak, Quercus obtusifolia.
 Red oak, Quercus rubra.
 Scarlet oak, Quercus coccinea.
 Scrub oak, Quercus ilicifolia, Quercus undulata, etc.
 Shingle oak, Quercus imbricaria.
 Spanish oak, Quercus falcata.
 Swamp Spanish oak, or Pin oak, Quercus palustris.
 Swamp white oak, Quercus bicolor.
 Water oak, Quercus aquatica.
 Water white oak, Quercus lyrata.
 Willow oak, Quercus Phellos.
     Among the true oaks in Europe are: Bitter oak, or Turkey oak, Quercus Cerris (see Cerris).
 Cork oak, Quercus Suber.
 English white oak, Quercus Robur.
 Evergreen oak, Holly oak, or Holm oak, Quercus Ilex.
 Kermes oak, Quercus coccifera.
 Nutgall oak, Quercus infectoria.
 Note: ☞ Among plants called oak, but not of the genus Quercus, are: African oak, a valuable timber tree (Oldfieldia Africana).
 Australian oak or She oak, any tree of the genus Casuarina (see Casuarina).
 Indian oak, the teak tree (see Teak).
 Jerusalem oak. See under Jerusalem.
 New Zealand oak, a sapindaceous tree (Alectryon excelsum).
 Poison oak, a shrub once not distinguished from poison ivy, but now restricted to Rhus toxicodendron or Rhus diversiloba.
 Silky oak or  Silk-bark oak, an Australian tree (Grevillea robusta).
 Green oak, oak wood colored green by the growth of the mycelium of certain fungi.
 Oak apple, a large, smooth, round gall produced on the leaves of the American red oak by a gallfly (Cynips confluens). It is green and pulpy when young.
 Oak beauty Zool., a British geometrid moth (Biston prodromaria) whose larva feeds on the oak.
 Oak gall, a gall found on the oak. See 2d Gall.
 Oak leather Bot., the mycelium of a fungus which forms leatherlike patches in the fissures of oak wood.
 Oak pruner. Zool. See Pruner, the insect.
 Oak spangle, a kind of gall produced on the oak by the insect Diplolepis lenticularis.
 Oak wart, a wartlike gall on the twigs of an oak.
 The Oaks, one of the three great annual English horse races (the Derby and St. Leger being the others).  It was instituted in 1779 by the Earl of Derby, and so called from his estate.
 To sport one's oak, to be “not at home to visitors,” signified by closing the outer (oaken) door of one's rooms. [Cant, Eng. Univ.]
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 Poi·son n.
 1. Any agent which, when introduced into the animal organism, is capable of producing a morbid, noxious, or deadly effect upon it; as, morphine is a deadly poison; the poison of pestilential diseases.
 2. That which taints or destroys moral purity or health; as, the poison of evil example; the poison of sin.
 Poison ash. Bot. (a) A tree of the genus Amyris (Amyris balsamifera) found in the West Indies, from the trunk of which a black liquor distills, supposed to have poisonous qualities. (b) The poison sumac (Rhus venenata). [U. S.]
 Poison dogwood Bot., poison sumac.
 Poison fang Zool., one of the superior maxillary teeth of some species of serpents, which, besides having the cavity for the pulp, is either perforated or grooved by a longitudinal canal, at the lower end of which the duct of the poison gland terminates. See Illust. under Fang.
 Poison gland Biol., a gland, in animals or plants, which secretes an acrid or venomous matter, that is conveyed along an organ capable of inflicting a wound.
 Poison hemlock Bot., a poisonous umbelliferous plant (Conium maculatum). See Hemlock.
 Poison ivy Bot., a poisonous climbing plant (formerly Rhus Toxicodendron, or Rhus radicans, now classified as Toxicodendron  radicans) of North America.  It is common as a  climbing vine, especially found on tree trunks, or walls, or as a low, spreading vine or as a shrub.  As a low vine it grows well in lightly shaded areas, recognizable by growing in clusters of three leaves.  Its leaves are trifoliate, rhombic-ovate, and variously notched.  Its form varies slightly from location to location, leading to some speculation that it may consist of more than one species.  Many people are poisoned by it, though some appear resistant to its effects.  Touching the leaves may leave a residue of an oil on the skin, and if not washed off quickly, sensitive areas of skin become reddened and develop multiple small blisters, lasting for several days to several weeks, and causing a persistent itch.  The toxic reaction is due to an oil, present in all parts of the plant except the pollen, called urushiol, the active component of which is the compound pentadecylacatechol (according to Charles">http://www.jaxmed.com/articles/Diseases/poison_ivy_dermatitis.htm">Charles H. Booras).   See Poison sumac.  It is related to poison oak, and is also called mercury.
 Poison nut. Bot. (a) Nux vomica. (b) The tree which yields this seed (Strychnos Nuxvomica). It is found on the Malabar and Coromandel coasts.
 Poison oak Bot., a dermatitis-producing plant often lumped together with the poison ivy (Toxicodendron  radicans) in common terminology, but more properly distinguished as the more shrubby  Toxicodendron  quercifolium (syn. Toxicodendron  diversilobum), common in California and Oregon.  Opinion varies as to whether the poison oak and poison ivy are only variants of a single species.  See poison ivy, above.
 Poison sac. Zool. Same as Poison gland, above. See Illust. under Fang.
 Poison sumac Bot., a poisonous shrub formerly considered to be of the genus Rhus (Rhus venenata), but now classified as Toxicodendron  vernix; -- also called poison ash, poison dogwood, and poison elder. It has pinnate leaves on graceful and slender common petioles, and usually grows in swampy places.  Both this plant and the poison ivy (Toxicodendron radicans, formerly Rhus Toxicodendron) have clusters of smooth greenish white berries, while the red-fruited species of this genus are harmless.  The tree (Rhus vernicifera) which yields the celebrated Japan lacquer is almost identical with the poison sumac, and is also very poisonous.  The juice of the poison sumac also forms a lacquer similar to that of Japan.
 Syn: -- Venom; virus; bane; pest; malignity.
 Usage: -- Poison, Venom. Poison usually denotes something received into the system by the mouth, breath, etc. Venom is something discharged from animals and received by means of a wound, as by the bite or sting of serpents, scorpions, etc. Hence, venom specifically implies some malignity of nature or purpose.

 poison oak
      n 1: dermatitis resulting from contact with a poison oak plant
      2: climbing plant common in eastern and central United States
         with ternate leaves and greenish flowers followed by white
         berries; yields an irritating oil that causes a rash on
         contact [syn: poison ivy, markweed, poison mercury,
         Toxicodendron radicans, Rhus radicans]