Cactaceae |
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Plants usually shrubs, subshrubs, or treelike, sometimes globose, solitary or clump-forming, erect to sprawling or, if epiphytic or epipetric, pendent, sometimes of a single, swollen internode, most of which maybe below ground level; stems usually succulent, photosynthetic, often jointed, the individual segments, termed cladodes, easily detached, sometimes individual plants comprised of one, globose internode; internodes smooth, tuberculate. and/or fluted, tubercles sometimes distinct or coalescent as longitudinal ribs, with areoles, highly modified shoots appeating as light to dark colored lumps usually with persistent spines plus, in members of subf. Opuntioideae, deciduous, glochids (retrorsely barbed bristles), and aboundant dense hairs. Leaves deciduous to persistent, vestigial or absent, spirally arranged, usually sessile, teret ot flat, usually 0-3(-10) cm long; spines flexible and hairlike to rigid and needlelike, terete to angled or flat, usually hard. Inflorescences usually of solitary flowers. Flowers usually bisexual, nocturnal or diurnal, usually sessile; perianths radially symmetric, deciduous or persistent; tepals 5-50 or more, intergrading gradually from sepal-like outer tepals to petal-like inner petals; stamens usually 50-1500+, sometimes fewer than 50, decurrent on inner surface of floral tube; ovaries compound, 1-celled, usually appearing inferior, placentation parietal; styles 1, with 3-14(-20+) lobes, the number equaling the number of placentae. Fruits basically berry-like, variable in succulence and peristence, succulent or leathery; seeds (0)5-3000+, yellowish, reddish, brown, black or appearing tand or whitish when covered by a tight-fitting arial. Cactaceae are native to the Americas where they grow but some members have become widely distributed, often as weeds, in tropical and subtropical regions of the Old World. One genusRhipsalis a tropical epiphytic species, is thought to have colonized Africa, Madagascar, and Sri Lanka without human asistance, its seeds being distributed by birds. Many cacti have been deliberately intoduced for food, fodder, horticulture and to support the formerly valuable production of cochineal. Unfortunately some have become significant weeds because of their ability to propagate vegetativly. Once established in areas used for grazing, the area loses much of its value. They have also been planted as green "fences".
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