Cacti [antikvár]

Introduction There are over 2,000 members of the Cactaceae, nearly all originating from North and South America, although a few belonging to the genus Rhipsalis are native to Africa. Several American species have been introduced to other continents where they have become naturalized. These succulent plants occupy habitats ranging from humid, tropical jungles to the driest deserts, and from just above sea-level, where the salt spray collects on the spines, beads and drops to the soil, to the tallest' mountains, where they may occasionally be covered by snow. Rela- tively few hve in true desert, i.e. where rainfall is less than 240mm (lin) per year, but a surprising variety has taken advantage of the tiny nooks and crannies available on rocky slopes. SHAPE AND SIZE Cacti species are extremely variable in size; the smallest, when mature, are the size of a thimble while the tallest of the tree-like species may reach 24m (80ft) in height. They are also extremely variable in shape and habit but can be broadly categorized as follows.