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Polypodiophyta

(Encyclopedia)Polypodiophyta pŏlˌēpōˌdēŏfˈətə [key], division of the plant kingdom consisting of the plants commonly called ferns. The ferns are vascular plants with stems, roots, and leaves. The small an...

endocytosis

(Encyclopedia)endocytosis ĕnˌdōsītōˈsəs [key], in biology, process by which substances are taken into the cell. When the cell membrane comes into contact with a suitable food, a portion of the cell cytoplasm...

Evans, Sir Martin John

(Encyclopedia)Evans, Sir Martin John, British geneticist, Ph.D., University College London, 1969. After serving on the faculty at University College London (1966–78) and Cambridge (1978–99), he became a profess...

leaf

(Encyclopedia)CE5 Microscopic cross section of the leaf blade CE5 Types of leaves leaf, chief food-manufacturing organ of a plant, a lateral outgrowth of the growing point of stem. The typical leaf consist...

tuber

(Encyclopedia)tuber, enlarged tip of a rhizome (underground stem) that stores food. Although much modified in structure, the tuber contains all the usual stem parts—bark, wood, pith, nodes, and internodes. The ey...

brain

(Encyclopedia)CE5 Brain brain, the supervisory center of the nervous system in all vertebrates. It also serves as the site of emotions, memory, self-awareness, and thought. Brain research, now often referred ...

immunity

(Encyclopedia)immunity, ability of an organism to resist disease by identifying and destroying foreign substances or organisms. Although all animals have some immune capabilities, little is known about nonmammalian...

vasectomy

(Encyclopedia)vasectomy, male sterilization by surgical excision of the vas deferens, the thin duct that carries sperm cells from the testicles to the prostate and the penis. Vasectomy is a popular method of birth ...

gall, in botany

(Encyclopedia)gall, abnormal growth, or hypertrophy, of plant tissue produced by chemical or mechanical (e.g., the rubbing together of two branches) irritants or hormones. Chemical irritants are released by parasit...

xylem

(Encyclopedia)xylem zīˈləm [key]: see stem; wood. ...