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A discipline that combines the means to know the location and heading of an aircraft with respect to some map or coordinate system, with guidance which means steering the aircraft along some desired path toward a destination. The construction of the…

An informal assemblage of predominantly aquatic organisms that carry out oxygen-evolving photosynthesis, but lack specialized water-conducting and food-conducting tissues. Algae (Fig. 1) may be either prokaryotic organisms (lacking an organized…

A natural process in which harmful or beneficial effects are caused by secondary metabolites that spread from a donor organism to a recipient and are produced by plants, algae, bacteria, and fungi. Allelopathy is a key ecological process and has…

A disease of the nervous system characterized by a progressive dementia that leads to profound impairment in cognition and behavior. Dementia occurs in a number of brain diseases where the impairment in cognitive abilities represents a decline from…

A psychiatric disorder in which a dramatic reduction in caloric intake consequent to excessive dieting leads to significant bodily, physiological, biochemical, emotional, psychological, and behavioral disturbances. Anorexia nervosa is one of three…

A group of distinct psychiatric disorders including generalized anxiety disorder, panic disorder, obsessive-compulsive disorder, social anxiety disorder, specific phobia, and posttraumatic stress disorder. Whereas fear is an adaptive emotion that is…

A neurodevelopmental condition that impairs the way that a person relates to and communicates with other people. Persons with autism have difficulties with social communication and interaction. They also can have unusual behaviors, such as…

Unwanted, aggressive behavior that involves a real or perceived power inequity. The behavior of bullying is often chronic and includes actions such as threats, spreading rumors, attacking someone physically or verbally, and purposefully excluding or…

A genus comprising yeasts that cause a variety of human diseases referred to as candidiasis. All Candida species are single-celled yeasts (fungal organisms) that are ovoid in shape and 3–5 μm in size, and they multiply by a process called budding.…

A general term for a genus of tall forage grasses, of which the most important species is the deeply rooted perennial Paspalum dilatatum. Dallis grass (see illustration) is widely grown in the southern United States, mostly for pasture, and remains…

An order of green algae (Chlorophyceae) in which the plant body (thallus) is composed of a nonseptate axis, attached by rhizoids and bearing whorls of branches. The walls utilize a partially crystalline mannan (polymer of mannose) as the skeletal…

The date palm, Phoenix dactylifera, which is one of the oldest cultivated tree crops. The date palm provides a staple food for many populations in the Middle East and North Africa and is also highly valued for feed, fiber, and shelter. Beginning in…

A subclass of the true mosses (Bryopsida) largely limited to the South Pacific. The subclass consists of a single genus, Dawsonia, of nine species. The gametophytes are remarkably similar to those of the Polytrichidae, but the origin and structure…

Woody higher plants that regularly lose their leaves at the end of each growing season. Dropping of the leaves occurs at the inception of an unfavorable season characterized by either cold or drought or both. Many woody plants of temperate climates…

A form of cognitive-behavioral therapy. Dialectical behavior therapy (DBT) is a psychotherapy developed by psychologist Marsha M. Linehan in the 1990s and designed originally to treat borderline personality disorder (BPD). DBT derives from a…

An order of flowering plants, division Magnoliophyta (Angiospermae), in the subclass Dilleniidae of the class Magnoliopsida (dicotyledons). The order has only a single family, the Diapensiaceae, with about 18 species of herbs and dwarf shrubs in…

A large group of flowering plants (angiosperms) that for many years has been considered one of the two main categories of plants, the other being monocotyledons. Dicotyledons have two seedling leaves as opposed to the single one in most…

A large and diverse order of the true mosses (Bryopsida), containing 13 families. Plants in the Dicranales generally have long, narrow leaves and deeply forked peristome teeth. The plants are erect and simple or merely forked and often woolly…

A genus of the plantain family (Plantaginaceae) or figwort family (Scrophulariaceae), whose dried leaves contain a number of glucosides that can be used as powerful cardiac stimulants and diuretics. The genus Digitalis ranges from the Canary Islands…

An annual culinary herb, genus Anethum, of the carrot family, Apiaceae (Umbelliferae). Dill supplies four products: dill seed oil, dill leaf oil, dill seed, and dill leaf. Although all dill grown in the United States is one species, Anethum…

An order of flowering plants, division Magnoliophyta (Angiospermae), class Magnoliopsida (dicotyledons), subclass Dilleniidae. The order Dilleniales consists of one family: the Dilleniaceae, which comprises about 350 species. (The family Paeoniaceae…

A large subclass of the class Magnoliopsida (dicotyledons) of the division Magnoliophyta (Angiospermae), the flowering plants, consisting of 13 orders, 78 families, and nearly 25,000 species. The subclass is morphologically ill-defined, but most of…

A large and extremely diverse class of biflagellate algae (dinoflagellates) in the chlorophyll a–c phyletic line (Chromophycota). In protozoological classification, these organisms constitute an order, Dinoflagellida, of the class Phytomastigophora.…

A widespread order of lilioid monocotyledons composed of four or five families, the most important of which is Dioscoreaceae (650 species). The families comprising the order Dioscoreales contain some of the most peculiar plants among the monocots.…

An order of flowering plants (angiosperms) in the asterid I group of the eudicotyledons consisting of around 6 families and almost 1000 species. Like many asterids of the asterid II group, Dipsacales have an inferior ovary and opposite leaves. They…

Any of the tree or shrub species in the genus Cornus. The tree, Cornus florida, also known as the flowering dogwood, may reach a height of 40 ft (12 m) and is found in the eastern half of the United States and in southern Ontario, Canada. It has…

The state in which a living plant organ (seed, bud, tuber, and bulb) fails to exhibit growth, even when environmental conditions are favorable. Environmental conditions favorable for growth usually include the presence of water and oxygen, and an…

A large coniferous tree, Pseudotsuga menziesii (formerly, P. taxifolia), known also as red fir, belonging to the pine family (Pinaceae). Douglas-fir is one of the most widespread and most valuable tree species of western North America and ranks…

An order of flowering plants, division Magnoliophyta (Angiospermae) in the subclass Dilleniidae of the class Magnoliopsida (dicotyledons). The order consists of 5 families and about 1750 species, the Sapotaceae (about 800 species) and Ebenaceae…

Any tree of the genus Diospyros of the ebony family, containing more than 250 species. Some species of ebony are important for their succulent fruits, such as date plum, kaki plum, and persimmon, and several are important for timber, particularly…

An obligate association formed between the roots of many plant species, especially trees, and a diverse range of soil fungi. The fungi and the finest, terminal root tips interact to form joint organs called ectomycorrhizas (Fig. 1). In…

Those organ systems of the animal body which mediate overt behavior. Injury to an effector system leads to loss or to subnormal execution of behavior patterns mediated by the system, conditions termed paralysis and paresis, respectively.Overt…

Any species of Ulmus, a genus of hardwood trees in the Northern Hemisphere, with simple, serrate, deciduous leaves. The American or white elm (U. americana) is the most important species (Fig. 1). It is a large, typically vase-shaped tree that…

One of the two plant subkingdoms, with the other being the Thallobionta. The Embryobionta (often also called Embryophyta) form a well-marked group with many morphological, anatomical, and physiological features in common, and taxonomists are agreed…

An order of the true mosses (subclass Bryidae) that grow in dull, dark tufts on soil or soil-covered rock, generally in calcareous areas. The Encalyptales consist of a single family and two genera, the better known being Encalypta, the extinguisher…

The single layer of plant cells that is located between the cortex and the vascular (xylem and phloem) tissues (Fig. 1). It has its most obvious development in roots and subaerial stems. In the aerial stem and in leaves it is not always detectable…

The outermost layer (occasionally several layers) of cells on the primary plant body. Its origin and structure are variable. In addition to a general description of the epidermis of plants, this article singles out five structural components of the…

An order of the division Sphenophyta, subkingdom Embryobionta. The Equisetales, commonly known as horsetails, is represented by a single living genus, Equisetum, with about 25 species found in both moist and dry habitats. These plants grow…

Ergot is the seedlike body of fungi (molds) of the genus Claviceps; ergotism is a complex disease of humans and certain domestic animals caused by ingestion of grains and cereals infested with ergot. Ingestion of these long, hard, purplish-black…

An order of flowering plants, division Magnoliophyta (angiosperms), in the large asterid assemblage (often Asteridae in previous systems of classification). Nearly all of the 24 families assigned to the order have previously been considered members…

An order of flowering plants, division Magnoliophyta (Angiospermae), subclass Commelinidae of the class Liliopsida (monocotyledons). The order consists of the single family Eriocaulaceae, with about 1200 species. The Eriocaulales are Commelinidae…

Volatile, fragrant oils obtained from plants. Essential oils are distinguished from those known as fixed oils, which are mainly triglycerides of fatty acids. Essential oils have been obtained from thousands of plants (Fig. 1) and are designated and…

The study of utilization of fungi by common people, as food or medicine, or in crafts, stories, or rituals. Ethnomycology is a subfield of ethnobotany (although, strictly speaking, fungi are not plants) or ethnobiology. Originally, emphasis was on…

A phytohormone (plant hormone) that is an important signaling molecule involved in many plant processes, including, but not limited to, abscission (the physiological process promoted by abscisic acid whereby plants shed a part), leaf and flower…

A large and important Australian forest tree, including about 700 species in the family Myrtaceae. Eucalyptus trees (eucalypts; genus Eucalyptus) occur throughout Australia and are particularly prevalent in eastern areas of the continent. However,…

An order of flowering plants, division Magnoliophyta (Angiospermae), in the subclass Hamamelidae of the class Magnoliopsida (dicotyledons). The order consists of a single family, genus, and species, Eucommia ulmoides, of China. It is a simple-leaved…

One of the two major types of flowering plants (angiosperms), characterized by possession of three apertures in their pollen; the other major type is magnoliids. Although this difference in pollen development and form has been known for a long time,…

An order of flowering plants, division Magnoliophyta (Angiospermae), in the subclass Rosidae of the class Magnoliopsida (dicotyledons). The order consists of the large family Euphorbiaceae (about 7500 species) and 3 small satellite families which…

Plants that retain their green foliage throughout the year. Popularly, needle-leaved trees (pine, fir, juniper, spruce) and certain broad-leaved shrubs (rhododendron, laurel) are called evergreens. In warm regions many broad-leaved trees (magnolia,…

An order of flowering plants, division Magnoliophyta (Angiospermae), in the subclass Rosidae of the class Magnoliopsida (dicotyledons). The order consists of three closely related families (Mimosaceae, Caesalpiniaceae, Fabaceae) collectively called…