Simon & Schuster's Guide to Cacti and Succulents

INTRODUCTION THE CACTACEAEIt has often been said that there can be no half measures in regard to cacti: people either love them or hate them. This assertion would appear to be borne out by the fact that on the one hand, many people find them unattractive, or indeed repulsive, because of their prickles, while on the other hand, there are innumerable associations of cactus lovers throughout the world -- for example, in New South Wales, Vienna, Zurich, Prague, Tokyo, Moscow and, naturally, Mexico City and El Centro, California.The fascination that people feel for cacti is as multifaceted as the plants themselves and as mysterious as their origins, and it is a fascination that deepens as one's knowledge of the plants increases. Comprising over 2,000 species, Cactaceae is the largest of the many plant families -- such as the euphorbias, crassulas, agaves, mesembryanthemums, milkweeds and lilies -- that are known as succulents because they store water in their leaves, stems and roots. (In other words, to clarify a point that puzzles many people, all cacti are succulents, but not all succulents are cacti.)The origins of the Cactaceae are thought to be very ancient in terms of the development of plant forms, although few succulent plants survive in fossilized form to tell us their history. The system of classification adopted by botanists for Cactaceae is based not only on the affinities between different genera but also on their presumed chronological development. It divides the cacti into four categories, as follows:1. Plants that still produce leaves in spite of the special characteristics of the cactus family2. Plants that produce leaves, but in most cases lose them very soon3. Plants with rudimentary leaves similar to scales, or with no leaves at all4. Plants with stems resembling leaves(cladodes),epiphytes or semi-epiphytesThis is a rational sequence based on the premise that succulent plants of families other than the Cactaceae lose their leaves because they have to adapt to dry climates, but it does not mean that cacti developed in precisely this way. Indeed they may well have been able to adapt contemporaneously to diverse climates. How and why the genusRhipsalis,which belongs to a family native to the Americas, came to grow wild in equatorial Africa, Madagascar, the Mascarene Islands and Ceylon is a mystery, although it is likely that the plant was introduced into these areas by birds which carried its sticky seeds to the Old World.All members of the Cactaceae are xerophytes in the broadest sense of the word: they are adapted for growth under dry conditions. In particular, they are designed to reduce moisture loss to a minimum, and they are capable of storing water in their tissues.In addition, all members of the family -- no matter what their shape -- have a characteristic that distinguishes them from all other plant families: they produceareoles.These round to oval structures ranging from 1/16 in. (1 1/2 mm.) to more than 1/2 in. (13 mm.) across are found in widely varying positions on the cacti. They are composed of two perpendicular buds. From the upper bud come either the flowers and subsequent fruits or the new branches, which consist of segments -- often called "joints," like the upper and lower joints of a chicken leg -- that are knotted tightly together at the base. From the lower bud come the spines. These may resemble a cluster of small, wicked daggers (sometimes with barbed ends); or the dagger-like spines may be surrounded by tiny bristles or prickles and/or curly wool or hair. One of the peculiarities of the cacti is that the spines -- like the thorns on roses -- are not connected to the tissues below them; consequently no real harm is done to a plant when a spine is torn off. By contrast, when a spine is removed from a succulent such asEuphorbia,the tissue beneath it is damaged.Cacti have numerous other distinSchuler, Stanley is the author of 'Simon & Schuster's Guide to Cacti and Succulents ' with ISBN 9780671602314 and ISBN 0671602314.