Cotton

The cotton plant belongs to the genus Gossypium of the family Malvaceae (mallow family). It is generally a shrubby plant having broad three-lobed leaves and seeds in capsules, or bolls; each seed is surrounded with downy fiber, white or creamy in color and easily spun. The fibers flatten and twist naturally as they dry.

Cotton is classified in the division Magnoliophyta, class Magnoliopsida, order Malvales, family Malvaceae.

Cotton is of tropical origin but is most successfully cultivated in temperate climates with well-distributed rainfall. It is planted annually by seed in furrows; the plants are thinned and weeded during the spring growing season. Diseases and insect pests are numerous; of these the most destructive has been the boll weevil, which has caused enormous losses. Genetically altered strains of cotton are being developed that can resist infestation by some insects and damage by application of herbicides.

Mechanical harvesting is preceded by a chemical-defoliant spray to remove the leaves, leaving only the cotton bolls. In the ginhouse the cotton is separated from the seeds by a cotton gin and then baled. The manufacture of cotton cloth involves many processes—carding, combing, and spinning—which transform raw fiber into yarn or thread strong enough for weaving.

Innumerable commodities are made from cotton. From the lint (the fiber separated from the seed) come the major products, chiefly textile and yarn goods, cordage, automobile-tire cord, and plastic reinforcing. The linters (short, cut ends removed from the seed after ginning) are a valuable source of cellulose. Cotton hulls are used for fertilizer, fuel, and packing; fiber from the stalk is used for pressed paper and cardboard.

Tobacco

Tobacco, name for any plant of the genus Nicotiana of the Solanaceae family (nightshade family) and for the product manufactured from the leaf and used in cigars and cigarettes, snuff, and pipe and chewing tobacco. Tobacco plants are also used in plant bioengineering, and some of the 60 species are grown as ornamentals. The chief commercial species, N. tabacum, is believed native to tropical America, like most nicotiana plants, but has been so long cultivated that it is no longer known in the wild. N. rustica, a mild-flavored, fast-burning species, was the tobacco originally raised in Virginia, but it is now grown chiefly in Turkey, India, and Russia. The alkaloid nicotine is the most characteristic constituent of tobacco and is responsible for its addictive nature. The possible harmful effects of the nicotine, tarry compounds, and carbon monoxide in tobacco smoke vary with the individual's tolerance.

Mistletoe

Mistletoe, common name for the Loranthaceae, a family of chiefly tropical hemiparasitic herbs and shrubs with leathery evergreen leaves and waxy white berries. They have green leaves, but they manufacture only part of the nutrients they require. Mistletoes are aerial hemiparasites, attaching themselves to their hosts by modified roots called haustoria, with which they absorb water and food from the host. The list of hosts is varied and numerous. Mistletoes are widely used for Christmas decoration. The custom of kissing under a branch of mistletoe apparently originated among the Druids and other early Europeans, to whom mistletoe was sacred. From early times it has been associated with folklore and superstition; it was thought to cure many ills. The mistletoe most widely sold in America is Phoradendron flavescens; most popular in Europe is the "true" mistletoe, Viscum album of the related family Viscacceae, which is parasitic especially on apple trees. An American genus (Arceuthobium) with several species found along the Pacific coast is parasitic on conifers. The largest genus of the family, Loranthus, is predominantly African. The mistletoe family is classified in the division Magnoliophyta, class Magnoliopsida, order Santalales.

Cone

Cone or strobilus (strŏb`ələs), in botany, reproductive organ of the gymnosperms (the conifers, cycads, and ginkgoes). Like the flower in the angiosperms (flowering plants), the cone is actually a highly modified branch; unlike the flower, it does not have sepals or petals. Usually separate male (staminate, or pollen) cones and female (ovulate, or seed) cones are borne on the same plant. Each of the numerous scales, or sporophylls, of the staminate cone bears pollen and each female-cone scale bears ovules in which egg cells are produced. In the pine, a conifer, the staminate cones are small and short-lived; they are borne in clusters at the top of the tree. At the time of pollination, enormous numbers of pollen grains are released and dispersed by wind; those that land accidentally on female-cone scales extend pollen tubes part way into the ovule during one growing season but usually do not reach the stage of actual fertilization until the next year. The cones that are commonly observed are the seed cones, which are normally hard and woody although in a few the scales are fleshy at maturity. The terms strobili and cones are also applied to the comparable and nonseed bearing structures of the horsetails and club mosses.

Pine

Pine, common name for members of the Pinaceae, a family of resinous woody trees with needlelike, usually evergreen leaves. The Pinaceae reproduce by means of cones (see cone) rather than flowers and many have winged seeds, suitable for wind distribution. They are found chiefly in north temperate regions, where they form vast forests. The family was apparently more abundant in the mid-Cenozoic era, but it has maintained its population better than other gymnosperms because the trees are more adaptable to cold, dry climates; the reduced leaf surface and deep-set stomata minimize loss of water by transpiration. The family is the largest and most important of the conifers, providing naval stores, paper pulp, and more lumber by far than any other family. In some localities almost pure stands occur, permitting economical lumbering of large numbers of a given type of tree. Of the family's nine genera four are widely dispersed throughout North America and the Old World. Members of all nine genera are represented in horticulture as introduced timber trees or ornamentals. The so-called kauri pine, although pinelike in appearance, belongs to another family

Nectarine

Nectarine, name for a tree (Prunus persica var. nectarina) of the family Rosaceae (rose family) and for its fruit, a smooth-skinned variety of the peach. The nectarine is a classical example of bud variation (see mutation). The nectarine tree occasionally produces peaches, and the peach tree nectarines. In appearance, culture, and care the nectarine is almost identical to the peach. It is cultivated in north temperate zones of both hemispheres, in America chiefly in the mild Pacific coastal area. The nectarine has been known for at least 2,000 years; in the 16th cent. it was called the nut of Persia. Nectarines are classified in the division Magnoliophyta, class Magnoliopsida, order Rosales, family Rosaceae.

Plant Differentiation From Other Kingdoms

Plants are multicellular eukaryotes—that is, their cells contain membrane-bound structures called organelles. Plants differ from other eukaryotes because their cells are enclosed by more or less rigid cell walls composed primarily of cellulose. The most important characteristic of plants is their ability to photosynthesize. During photosynthesis, plants make their own food by converting light energy into chemical energy—a process carried out in the green cellular organelles called chloroplasts (see Chlorophyll; Chloroplast). A few plants have lost their chlorophyll and have become saprophytes or parasites—that is, they absorb their food from dead organic matter or living organic matter, respectively—but details of their structure show that they are evolved plant forms.

Fungi, also eukaryotic and long considered members of the plant kingdom, have now been placed in a separate kingdom because they lack chlorophyll and plastids and because their rigid cell walls contain chitin rather than cellulose. Unlike the majority of plants, fungi do not manufacture their own food; instead they are saprophytic, absorbing their food from either dead or living organic matter.

The various groups of algae were also formerly placed in the plant kingdom because many are eukaryotic and because most have rigid cell walls and carry out photosynthesis. Nonetheless, because of the variety of pigment types, cell wall types, and physical attributes found in the algae, they are now recognized as part of two separate kingdoms, containing a diversity of plantlike and other organisms that are not necessarily closely related. One of the phyla of algae, the green algae, is believed to have given rise to the plant kingdom, because its chlorophylls, cell walls, and other details of cellular structure are similar to those of plants.

The animal kingdom is also multicellular and eukaryotic, but its members differ from the plants in deriving nutrition from other organic matter; by ingesting food rather than absorbing it, as in the fungi; by lacking rigid cell walls; and, usually, by having sensory capabilities and being motile, at least at some stage. See Classification.