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psychosis (psychology)
any of several major mental illnesses that can cause delusions, hallucinations, serious defects in judgment and other cognitive processes, and the inability to evaluate reality objectively. A brief treatment of psychosis follows. For full treatment, see mental disorder...
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psychosomatic disorder (pathology)
condition in which psychological stresses adversely affect physiological (somatic) functioning to the point of distress. It is a condition of dysfunction or structural damage in bodily organs through inappropriate activation of the involuntary nervous system and the glands of internal secretion. Thus, the psychosomatic sympt...
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Psychosomatic Medicine: Its Principles and Applications (work by Alexander)
...who conducted extensive research on emotional disturbance and psychosomatic disease, identifying various disorders with particular unconscious conflicts. This work is represented in his book Psychosomatic Medicine: Its Principles and Applications (1950)....
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psychosurgery (medicine)
the treatment of psychosis or other mental disorders by means of brain surgery....
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psychotherapy (psychology)
any form of treatment for psychological, emotional, or behaviour disorders in which a trained person establishes a relationship with one or several patients for the purpose of modifying or removing existing symptoms and promoting personality growth. Psychotropic medications may be used as adjuncts to treatment, but the healing influence in psychotherapy is produced primarily by the words and actio...
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psychotherapy: Year In Review 1994
In 1994 the mental health profession found itself deeply divided over an approach to psychotherapy known as "repressed memory therapy," or RMT. RMT relies on so-called memory-recovery techniques to help a patient "remember" or "recover" episodes, usually of sexual abuse, from childhood--episodes that presumably have been "forgotten." The abuse is assumed to be an underlying caus...
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psychotomimetic drug
any of the so-called mind-expanding drugs that are able to induce states of altered perception and thought, frequently with heightened awareness of sensory input but with diminished control over what is being experienced. See also hallucinogen....
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psychotropic drug
To consider drugs only as medicinal agents or to insist that drugs be confined to prescribed medical practice is to fail to understand man. The remarks of the American sociologist Bernard Barber are poignant in this regard:Not only can nearly anything be called a “drug,” but things so called turn out to have an......
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Psychrolutidae (fish)
...to about 20 cm (8 inches). Freshwater, endemic to Lake Baikal in Russia. 1 genus (Comephorus) with 2 species.Family Psychrolutidae (fathead sculpins) Body naked, with loose skin, or with plates bearing prickles; lateral line reduced; pelvic fin with one spine and three soft rays; vertebrae ...
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psychrometer (instrument)
a hygrometer composed of two similar thermometers. The bulb of one thermometer is kept wet (by means of a thin, wet cloth wick) so that the cooling that results from evaporation makes it register a lower temperature than the dry-bulb thermometer. When readings are taken simultaneously, it is possible (with the use of psychrometric tables) to determine the ...
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psychrophile (microorganism)
Bacteria have adapted to a wide range of temperatures. Bacteria that grow at temperatures of less than about 15 °C (59 °F) are psychrophiles. The ability of bacteria to grow at low temperatures is not unexpected, since the average subsurface temperature of soil in the temperate zone is about 12 °C (54 °F) and 90 per...
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psykter (pottery)
ancient Greek pottery vessel with a tall, cylindrical foot, rounded body, and short neck, used for cooling wine. Filled with wine, it could be placed inside a larger vessel, such as a krater, which had been filled with snow; or the psykter itself might be filled with snow and placed inside a larger vessel containing the wine....
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Psyllidae (insect)
any member of the approximately 2,000 species of the insect family Psyllidae (order Homoptera). The jumping plant louse is about the size of a pinhead. Its head, long antennae and legs, and transparent wings resemble, on a reduced scale, the features of the cicada. Eggs are deposited on leaves or twigs of the host plant; the nymphs, flattened and broadly ovate, usually feed clustered together. So...
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Psyllophryne didactyla (frog)
Although all frogs are readily recognizable, there are great varieties of sizes and of structural modifications. Many frogs are tiny animals; perhaps the smallest is the Brazilian Psyllophryne didactyla, adults of which measure 9.8 mm (0.4 inch) or less in body length (with legs drawn in), whereas the West African goliath frog, ......
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Psysh, Mount (mountain, Russia)
...salt marshes and lagoons line the Azov coast. The southern third of the region is occupied by the western Caucasus, which reach 12,434 feet (3,790 metres) at Mount Psysh (in the neighbouring Karachay-Cherkessia republic) and fall gradually in height westward as they run parallel to the Black Sea, from which they are separated by a narrow ......
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psywar
the use of propaganda against an enemy, supported by such military, economic, or political measures as may be required. Such propaganda is generally intended to demoralize the enemy, to break his will to fight or resist, and sometimes to render him favourably disposed to one’s position. Propaganda is also used to strengthen the resolve of allies or resistance fighters. Th...
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Pszczyna (Poland)
city, Śląskie województwo (province), southern Poland, situated on the Pszczynka River, a tributary of the Vistula River. A cultural and historic site, the city is known for its fine lace and collection of Siles...
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pt (measurement)
unit of capacity in the British Imperial and U.S. Customary systems of measurement. In the British system the units for dry measure and liquid measure are identical; the single British pint is equal to 34.68 cubic inches (568.26 cubic cm) or one-eighth gallon. In the United States the un...
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Pt (chemical element)
chemical element, the best known and most widely used of the six platinum metals of Groups 8–10 (VIIIb), Periods 5 and 6, of the periodic table. A very heavy, precious, silver-white metal, platinum is soft and ductile and has ...
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PT boat
In the 1930s the German, Italian, British, and U.S. navies regained interest in motor torpedo boats, which had been largely discarded after World War I. All four navies built them in substantial numbers to fight in narrow seas during World War II. Against convoys in the English Channel and the North Sea, the Germans used their S-boats......
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PTA (biochemistry)
Hemophilia may also be attributed to a deficiency of factor IX (hemophilia B) or of factor XI (hemophilia C); hemophilia B (also called Christmas disease), like hemophilia A, is sex-linked and occurs almost only in males, whereas hemophilia C may be transmitted by both males and......
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PTA (American organization)
American organization concerned with the educational, social, and economic well-being of children. The PTA was founded on Feb. 17, 1897, as the National Congress of Mothers; membership was later broadened to include teachers, fathers, and other citizens. There are 52 state branches, including one in the District of Columbia and one in Europe to serve American dependents on military bases. Within t...
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Ptacek, Stephen (American pilot)
...Base, in Kent, Eng., a distance of 160 miles (258 km), in 5 hr 23 min at an average speed of about 30 miles per hour (48 km/h) and a cruising altitude of 11,000 feet (3,350 m). The pilot was Stephen Ptacek, weighing 122 pounds (55 kg). The plane, powered by 16,128 solar cells connected to two ......
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Ptah (Egyptian god)
in Egyptian religion, creator-god and maker of things, a patron of craftsmen, especially sculptors; his high priest was called “chief controller of craftsmen.” The Greeks identified Ptah with Hephaestus (Vulcan), the divine blacksmith. Ptah was originally the local deity of Memphis, capital of Egypt from the ...
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Ptahhotep (Egyptian vizier)
vizier of ancient Egypt who attained high repute in wisdom literature. His treatise “The Maxims of Ptahhotep,” probably the earliest large piece of Egyptian wisdom literature available to modern scholars, was written primarily for young men of influential f...
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ptarmigan (bird)
any of three or four species of partridgelike grouse of cold regions, belonging to the genus Lagopus of the grouse family, Tetraonidae. They undergo seasonal changes of plumage, from white against winter snowfields to gray or brown, with barring, in spring and summer against tundra vegetation. Ptarmigan differ from other members of the grouse family in having the toes covered with stiff fea...
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PTC (medicine)
...Various techniques that combine contrast agents (dyes) with X-ray imaging are also used to determine whether the bile duct or other ducts within the pancreas are blocked. One example is called percutaneous transhepatic cholangiography (PTC), in which a needle is used to inject a dye directly into the liver, followed by X-ray imaging. Other X-ray imaging techniques include angiography, in......
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PTC (biochemistry)
Hemophilia may also be attributed to a deficiency of factor IX (hemophilia B) or of factor XI (hemophilia C); hemophilia B (also called Christmas disease), like hemophilia A, is sex-linked and occurs almost only in males, whereas hemophilia C may be transmitted by both males and......
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PTC tasting (biology)
a genetically controlled ability to taste phenylthiocarbamide (PTC) and a number of related substances, all of which have some antithyroid activity. PTC-tasting ability is a simple genetic trait governed by a pair of alleles, dominant T for tasting and recessive t for nontasting. Persons with genotypes TT and Tt are tasters, and persons with genotype tt are nonta...
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PTCA (medicine)
When coronary arteriography reveals relatively isolated, incompletely obstructive lesions, there are two alternative treatments—medication or coronary angioplasty (balloon dilation of the localized obstruction by a special catheter). When coronary arteriography reveals a severe blockage of the left main coronary artery or proximally in one or more of the major arteries, coronary artery......
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Ptelea trifoliata (tree)
(species Ptelea trifoliata), tree, of the rue family (Rutaceae), native to eastern North America. It has small, greenish white flowers; strong-smelling leaves in groups of three leaflets; and buff-coloured, wafer-shaped, winged fruits. The hop ...
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Ptenoglossa (gastropod superfamily)
...globular predators on burrowing bivalves: bore a hole in the clamshell using acid secretions, then insert the radula to feed; common in most oceans.Superfamily Ptenoglossa (Scalacea)Wentletraps (Epitoniidae) live in shallow to deep ocean waters; purple snails (Janthinidae) float on the ocean surface after building a raft ...
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Pteranodon (paleontology)
flying reptile (pterosaur) found as fossils in North American deposits dating from about 90 million to 100 million years ago during the Late Cretaceous Period. Pteranodon had a wingspan of 7 metres (23 feet) or more, and its toothless jaws were very long and pelican-like....
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Pteraspis (paleontology)
genus of extinct jawless fishlike vertebrates found as fossils in Early Devonian rocks (those 398 million to 416 million years old) in North America and Europe. Pteraspis was approximately 16 cm (6.5 inches) in length and had a heavy, rounded, bony shield that covered the anterior parts of the body. The remainder of t...
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Pteraster (sea star)
...S. endeca is 10-rayed and sometimes 50 cm across; the very common spiny sun star (Crossaster papposus) has as many as 15 arms. Cushion stars, of the circumboreal genus Pteraster, are plump five-rayed forms with raised tufts of spines and webbed, short, blunt arms....
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Pteria (ancient city, Turkey)
ancient capital of the “White Syrians” of northern Cappadocia in eastern Anatolia, which, according to the Greek historian Herodotus, was taken, enslaved, and ruined by the Lydian king Croesus (547 bc). The exact location of Pteria is unknown. The identification of Pteria with the ruins near modern Boğazköy is uncertain. Since, accordin...
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Pteria (oyster genus)
Bivalves of the genera Pinctada and Pteria have been collected in many tropical seas for the natural pearls they may contain, although in many countries, most notably Japan, pearl oyster fisheries have been developed. The windowpane oyster, Placuna placenta, has......
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Pteria penquin (oyster)
...activity, pearl farms now generally use a vessel as an operating platform. Immature pearl oyster shells (usually Pinctada fucata or Pteria penguin in Japan and Pinctada maxima in Australia) are reserved in barrels until maturation (2 to 3 years) and, when the shells reach certain size, are implanted with a......
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Pterichthys (paleontology)
...of extinct, mainly freshwater, jawed fishes, class Placodermi, abundant during Middle and Late Devonian times (387 to 360 million years ago). Members of such genera as Bothriolepis and Pterichthys were representative. Antiarchs were small and weak-jawed and had closely set eyes on top of the head. Armour shields covered the front part of the body as in the earliest known......
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Pteridaceae (plant family)
the maidenhair fern family, containing about 50 genera and approximately 950 species, in the division Pteridophyta (the lower vascular plants). Members of Pteridaceae are distributed throughout the world, especially in tropical and warm-temperate regions. The family is characterized by spore-producing structures (sporangia) located in lines ...
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pteridine (chemical compound)
The biological significance of pteridine compounds (from Greek pteron, “wing”) has become apparent since the first known members of the group were discovered as pigments of butterfly wings. One example is the yellow pigment 2-amino-4,6-pteridinedione (xanthopterin)....
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Pteridium (fern genus)
...(cup ferns, bracken)Plants mostly in soil, occasionally climbing; rhizomes mostly very long-creeping (to more than 100 metres [330 feet], in Pteridium), hairy; leaves two to four times pinnately compound, glabrous or hairy; sori mostly marginal or submarginal, discrete or in a more or less uninterrupted line, the indusium...
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Pteridium aquilinum (fern)
a member of the fern family Dennstaedtiaceae (plant division Pteridophyta), widely distributed throughout the world in temperate and tropical regions. Pteridium aquilinum is usually separated into 12 varieties or subspecies. Some botanists classify most or all of these varieties as separate species,...
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pteridophyll (leaf)
This species has a perennial black rootstock that creeps extensively underground and at intervals sends up fronds. Individual rhizomes have been documented as spreading up to about 400 metres (1,300 feet) in length, making bracken one of the largest plants in the world. The fronds may reach a height of 5 metres (16 feet) or more and, despite dying in autumn, often remain standing throughout the......
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Pteridophyta (biology)
any of the spore-bearing vascular plants, including the ferns, club mosses, spike mosses, quillworts, horsetails, and whisk ferns. Once considered of the same evolutionary line, ...
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pteridophyte (biology)
any of the spore-bearing vascular plants, including the ferns, club mosses, spike mosses, quillworts, horsetails, and whisk ferns. Once considered of the same evolutionary line, ...
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pteridosperm (plant)
loose confederation of seed plants from the Carboniferous and Permian periods (about 360 to 250 million years ago). Some, such as Medullosa, grew as upright, unbranched woody trunks topped with a crown of large fernlike fronds; others, such as Callistophyton, were woody vines. All had fernl...
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Pteridospermophyta (plant)
loose confederation of seed plants from the Carboniferous and Permian periods (about 360 to 250 million years ago). Some, such as Medullosa, grew as upright, unbranched woody trunks topped with a crown of large fernlike fronds; others, such as Callistophyton, were woody vines. All had fernl...
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pterin (chemical compound)
Closely related to the purines and formerly classed among them are the pterins, so named from their notable appearance in and first chemical isolation from the wings of certain butterflies. Both purines and pterins contain a six-atom pyrimidine ring; in purines this ring is chemically condensed with an imidazole ring; pterins contain the pyrazine ring. Pterins occur as white, yellow, orange, or......
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Pterioida (bivalve order)
...mantle margin lacking fusions; foot creeping; typically byssate; marine, estuarine, rarely freshwater; endobyssate and epibyssate. About 250 species.Order Pterioida (pearl oysters and fan shells)Shell equivalve, variably shaped; anisomyarian but often monomyarian; shell structure of outer simple.....
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Pteriomorphia (mollusk subclass)
...represented today by the superfamily Trigonioidea (placed in the subclass Palaeoheterodonta), which are an aberrant group of the subclass Pteriomorphia. The remaining, more typical, members of the Pteriomorphia also arose at this time and persist today, still characteristically occupying a range of substrate types but with byssal attachment and a trend toward loss of the anterior adductor......
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Pteris (fern genus)
The Pteridoid clade contains 17 genera and about 400 species. The largest genus, Pteris (brakes), consists of about 250 species distributed throughout tropical and warm temperate parts of the world and is known for the large number of hybrids between various species. Pityrogramma, or the gold- and silver-backed ferns, consists of about 16 tropical species, which are occasionally......
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pterobranch (invertebrate)
any small marine invertebrate of the class Pterobranchia (phylum Hemichordata). Pterobranchs are found mainly in the Southern Hemisphere, but a few species occur in northern waters. The pterobranch body, like that of the related acorn worm, can be divided into three regions: a proboscis (i.e., a tubular sucking organ); a collar with tentacles used to filter food, usually ...
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Pterobranchia (invertebrate)
any small marine invertebrate of the class Pterobranchia (phylum Hemichordata). Pterobranchs are found mainly in the Southern Hemisphere, but a few species occur in northern waters. The pterobranch body, like that of the related acorn worm, can be divided into three regions: a proboscis (i.e., a tubular sucking organ); a collar with tentacles used to filter food, usually ...
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Pterocarpus dalbergioides (plant)
...equaled by any other timber. A small chip of the wood placed in water soon takes on an opalescent colour because of a substance in the wood cells. Narra wood is known also as Burmese rosewood, Andaman redwood, and kiabooca wood....
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Pterocarpus indicus (tree)
...timber trees of the genus Pterocarpus of the pea family (Fabaceae or Leguminosae). The name refers especially to P. indicus, or India padauk, or the hard wood, noted for its ability to take a high polish, that is derived from the trees. Narra wood is used for cabinetwork; it is usually red or rose colour, often variegated......
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Pterocarpus macrocarpus (plant)
...colouring being hardly equaled by any other timber. A small chip of the wood placed in water soon takes on an opalescent colour because of a substance in the wood cells. Narra wood is known also as Burmese rosewood, Andaman redwood, and kiabooca wood....
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Pterocarpus santalinus (tree)
Many other woods are used as substitutes for true sandalwood. Red sandalwood is obtained from the reddish-coloured wood of Pterocarpus santalinus, a Southeast Asian tree of the pea family (Fabaceae). This species may have been the source of the sandalwood used in King Solomon’...
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Pterocarya (plant)
(genus Pterocarya), any of about six species of Asian trees of the walnut family (Juglandaceae). They often are 30 m (about 100 feet) tall and bear winged, edible, one-seeded nuts. One species, P. stenoptera, is planted as an ornamental. The wood of some species is used in cabinetmaking....
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Pterocarya stenoptera (tree)
...Pterocarya), any of about six species of Asian trees of the walnut family (Juglandaceae). They often are 30 m (about 100 feet) tall and bear winged, edible, one-seeded nuts. One species, P. stenoptera, is planted as an ornamental. The wood of some species is used in cabinetmaking....
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Pterocletidae (bird)
any of 16 species of birds of Asian and African deserts. According to some systems of classification, sandgrouse are ranked with the plovers within the order Charadriiformes....
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Pteroclidae (bird)
any of 16 species of birds of Asian and African deserts. According to some systems of classification, sandgrouse are ranked with the plovers within the order Charadriiformes....
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Pteroclididae (bird)
any of 16 species of birds of Asian and African deserts. According to some systems of classification, sandgrouse are ranked with the plovers within the order Charadriiformes....
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Pteroclidiformes (bird)
any of 16 species of birds of Asian and African deserts. According to some systems of classification, sandgrouse are ranked with the plovers within the order Charadriiformes....
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Pterocnemia pennata (bird)
...America and are related to the ostrich and emu. The common rhea (Rhea americana; see photograph) is found in open country from northeastern Brazil southward to Argentina, while Darwin’s rhea (Pterocnemia pennata) lives from Peru southward to Patagonia, at the tip of the continent. Both species are c...
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pterodactyl (fossil reptile)
informal term for a subgroup of flying reptiles (Pterosauria) known from the Late Jurassic through Late Cretaceous periods (145 million to 65 million years ago)....
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Pterodactylus (fossil reptile)
informal term for a subgroup of flying reptiles (Pterosauria) known from the Late Jurassic through Late Cretaceous periods (145 million to 65 million years ago)....
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Pterodroma cahow (bird)
Some of the better known gadfly petrels are the endangered Bermuda petrel, or cahow (Pterodroma cahow, sometimes considered a race of P. hasitata); the dark-rumped petrel, also called the Hawaiian petrel (P. phaeopygia), another ......
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Pterodroma hasitata (bird)
...For nearly 300 years the species was believed extinct, but in 1951 a few pairs were discovered nesting on an offshore islet, where a remnant now survives under strict protection. The related black-capped petrel, or diablotin (P. hasitata), of the West Indies was also thought extinct (because of predation by humans, rats, and mongooses) until in 1961 a substantial population,......
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Pteroglossus (bird)
any of certain toucan species. See toucan....
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Pterois (fish)
(Pterois), any of several species of showy Indo-Pacific fish of the scorpion fish family, Scorpaenidae (order Scorpaeniformes). Lion-fish are noted for their venomous fin spines, which are capable of producing painful, though rarely fatal, puncture wounds. The fishes have......
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Pterois volitans (fish)
...of bold, zebralike stripes. When disturbed, the fish spread and display their fins and, if further pressed, will present and attack with the dorsal spines. One of the best-known species is Pterois volitans, an impressive fish sometimes kept by fish fanciers. It is striped with red, brown, and white and grows to about 30 cm (12 inches) long....
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Pteromyinae (rodent)
any of 43 species of gliding squirrels. Two species are North American, two live in northern Eurasia, and all others are found in the temperate and tropical forests of India and Asia. Although these rodents do not fly, glides of up to 450 metres (almost 1,500 feet) have been recorded for Oriental giant flying squirrels (Petaurista...
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Pteronotus personatus (mammal)
...pulse duration varies with the species and the situation. During cruising flight the pulses of the greater false vampire bat (Megaderma lyra) are 1.5 milliseconds (0.0015 second), those of Wagner’s mustached bat (Pteronotus personatus) 4 milliseconds, and those of the greater horseshoe bat (......
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Pteronura brasiliensis (mammal)
rare South American species of otter....
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Pterophoridae (insect)
any of about 1,000 species of delicate moths (order Lepidoptera) that are named for the deep wing divisions that resemble plumes or lobes. The clefts in the wings divide them for about half their length, with the forewings usually divided into two plumes and the hindwings into three. The plume moths differ from the ...
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Pterophoroidea (insect superfamily)
...at least 2 years to mature; some very destructive, including the coffee borer (Zeuzera coffeae) and leopard moth (Z. pyrina).Superfamily PterophoroideaAlmost 1,000 species in 1 family.Family Pterophoridae (plume moths)...
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Pterophyllum altum (fish)
...dorsal, anal, and pelvic fins. Depending on the authority, one to three species may be recognized: P. scalare, P. eimekei, and P. altum. Angelfishes are native to the freshwaters of tropical South America and may grow to a length of about 15 cm (6 inches). They are....
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Pterophyllum eimekei (fish)
...fishes with elongated dorsal, anal, and pelvic fins. Depending on the authority, one to three species may be recognized: P. scalare, P. eimekei, and P. altum. Angelfishes are native to the freshwaters of tropical South America and may grow to a length of about 15 cm...
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pteropod (mollusk)
small marine gastropods of the subclass Opisthobranchia (phylum Mollusca) characterized by a foot modified to form a pair of winglike flaps (parapodia) that are used for swimming. They live at or near the sea surface; most are less than 1 cm (0.4 inch) long....
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pteropod ooze (marine deposit)
...made of silica) and then are divided again according to the predominant skeleton type. Thus, the calcareous oozes include globigerina ooze, containing the shells of planktonic foraminifera, and pteropod ooze, made up chiefly of the shells of pelagic mollusks. The siliceous oozes include radiolarian ooze, comprising essentially brown clay......
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pteropodid (mammal)
any of more than 180 species of large-eyed fruit-eating or flower-feeding bats widely distributed from Africa to Southeast Asia and Australia. Some species are solitary, some gregarious. Most roost in the open in trees, but some inhabit caves, rocks, or buildings....
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Pteropodidae (mammal)
any of more than 180 species of large-eyed fruit-eating or flower-feeding bats widely distributed from Africa to Southeast Asia and Australia. Some species are solitary, some gregarious. Most roost in the open in trees, but some inhabit caves, rocks, or buildings....
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pteropsid (plant)
any of a group of vascular plants (tracheophytes) that includes ferns, extinct seed ferns, gymnosperms (conifers, etc.), and angiosperms (flowering plants). Pteropsids manifest a...
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Pteropsida (plant)
any of a group of vascular plants (tracheophytes) that includes ferns, extinct seed ferns, gymnosperms (conifers, etc.), and angiosperms (flowering plants). Pteropsids manifest a...
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Pteroptochidae (bird family)
family of Latin American birds, based on the genus Pteroptochas—in this encyclopaedia classified as part of the tapaculo family (Rhinocryptidae)....
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Pteropus (mammal)
any of about 65 bat species found on tropical islands from Madagascar to Australia and Indonesia and mainland Asia. They are the largest bats; some attain a wingspan of 1.5 m (5 feet), with a head and body length of about 40 cm (16 inches)....
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Pteropus conspicillatus (bat)
any of about 65 bat species found on tropical islands from Madagascar to Australia and Indonesia and mainland Asia. They are the largest bats; some attain a wingspan of 1.5 m (5 feet), with a head and body length of about 40 cm (16 inches).......
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Pteropus giganteus (mammal)
...pubic nipples, which the infant may hold in its mouth when its mother flies. The infants are nourished by milk for a period of about five or six weeks in many small bats and for five months in the Indian flying fox (Pteropus giganteus). By two months of age, most smaller bats have been flying and foraging for three or four weeks......
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pterosaur (fossil order)
any of the flying reptiles that flourished during all periods (Triassic, Jurassic, and Cretaceous) of the Mesozoic Era (251 million to 66 million years ago). Although pterosaurs are not dinosaurs, both are archosaurs, or “ruling reptiles,” a group to wh...
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Pterosauria (fossil order)
any of the flying reptiles that flourished during all periods (Triassic, Jurassic, and Cretaceous) of the Mesozoic Era (251 million to 66 million years ago). Although pterosaurs are not dinosaurs, both are archosaurs, or “ruling reptiles,” a group to wh...
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Pterostylis (plant)
(genus Pterostylis), any of almost 100 species of orchids (family Orchidaceae) native to Australasia. Greenhoods have dull-coloured, hooded flowers that trap insects. The lip of the flower is hinged and seals the entrance route of an insect that enters the flower to obtain its sweet nectar. The insect must leave by means of a special tunnel through the column that is lined with hairs. Pack...
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Pterostylis banksii (plant)
...insect as it escapes, and the pollen is thus carried to other flowers. Some species of greenhoods are commonly known as shell orchids. The jug orchid (P. recurva) is named for its shape. The hooded orchid (P. banksii) is native to New Zealand, and the closely related P. baptisii is from neighbouring Australia....
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Pterostylis baptisii (plant)
...jug orchid (P. recurva) is named for its shape. The hooded orchid (P. banksii) is native to New Zealand, and the closely related P. baptisii is from neighbouring Australia....
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Pterostylis coccinea (plant)
(genus Pterostylis), any of almost 100 species of orchids (family Orchidaceae) native to Australasia. Greenhoods have dull-coloured, hooded flowers that trap insects. The lip of the flower is hinged and seals the entrance route of an insect that enters the flower to obtain its sweet nectar. The insect must leave by means of a special tunnel through the column that is lined with hairs. Pack...
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Pterostylis recurva (plant)
...grains become attached to the insect as it escapes, and the pollen is thus carried to other flowers. Some species of greenhoods are commonly known as shell orchids. The jug orchid (P. recurva) is named for its shape. The hooded orchid (P. banksii) is native to New Zealand, and the closely related......
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Pterostyrax (plant genus)
genus of about four species of deciduous trees or shrubs, of the storax family (Styracaceae), native to East Asia. A few species, notably P. hispidus and P. corymbosus, both of which are called the epaulette tree, are cultivated in other regions as ornamentals. The genus is ...
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Pterostyrax corymbosus (tree)
...storax family (Styracaceae), native to East Asia. A few species, notably P. hispidus and P. corymbosus, both of which are called the epaulette tree, are cultivated in other regions as ornamentals. The genus is characterized by alternate stalked leaves and fragrant white flowers......
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Pterostyrax hispidus (tree)
...shrubs, of the storax family (Styracaceae), native to East Asia. A few species, notably P. hispidus and P. corymbosus, both of which are called the epaulette tree, are cultivated in other regions as ornamentals. The genus is characterized by alternate stalked leaves and......
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pteroylglutamic acid (vitamin)
water-soluble vitamin of the B complex that is essential in animals and plants for the synthesis of nucleic acids. Folic acid was isolated from liver cells in 1943....
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