Form and variety

Most of the Crassulaceae are herbaceous perennials, but a few are annual (Sedum coeruleum) or biennial (S. pilosum. sem-pervivoides 10.13). The largest. Crassula arborescens (9.3) and argentea. form small trees with fat. fleshy trunks 2m (6 ft) or more in height. Almost caudici-form is Cotyledon paniculata the botter-boom of southern Africa, with a massive gnarled trunk and more or less deciduous leaves. It has a close parallel in the giant Mexican stonecrops Sedum frutescens and S. oxypetalum....

Origin and diversity

How succulence originated is not yet clearly understood, although we know that it has happened independently in widely dissimilar groups of plants, as Fig. 1.6 shows. Experiments have shown lence in Tradescantia by causing the cells in the leaf to elongate vertically, and a similar enhanced fleshiness can be induced in Kalanchoe by reducing the day length by periodic shadings. Not all succulents are comparable in habitat and behaviour. We find one type of succulence in plants of the seashore...

Fouquieriaceae

This tiny Family of one genus and eight species is endemic to Mexico. The plants are extremely xerophytic hard-wooded shrubs with a tendency to enlargement at the base that reaches a climax in the unique 'Cirio' or 'Boojum' of Baja California, F. (Idria) columnaris (21.13). The tall, mostly unbranched trunk looks like a huge inverted turnip, and bears wiry side branches with tiny short-lived leaves that leave a spine when they detach from the woody stalk. F. columnaris has proved long-lived and...

Compositae

This, arguably the largest of all plant Families with an estimated 900 genera and over 13,000 species, owes its success to the highly efficient pollination and dispersal mechanisms described and figured in Chapters 4 and 15. Although the standardized head of small flowers surrounded by bracts is more or less constant and at once recognizable Lett (9.1) A succulent-leaved relative ot the popular house-plant. Coleus pentheri tolerates much drier conditions and is at home in a 9cm (3 in) pot Note...

Misers for water

Succulence is more than just an expansion of stems and leaves as water stores plants with middle-age spread as a revered botanist once described them to me. A storeroom for water is of no use if it lacks a door to prevent the contents from escaping. The external features that distinguish succulents from other plants are discussed in the next chapter. Internally, the succulent tissue has a distinctive look (1.3, 2.5), with large, thin-walled cells and conspicuous air spaces, suggestive of a...

Soil or nosoil

Soil mixtures recommended for succulents are legion. One book tabulates 25 for cacti alone. AU of them are presumably based upon the author's intuition, because no experimental evidence is cited, and none in the least resembles the soil in which I have seen cacti growing in nature. The prospective newcomer may well close such a book indespairand settle fora less exacting hobby. In practice, however, most growers use a single compost throughout, with only minor modifications for epiphytes (which...

Cultivation

A generous sampling of the cactus Family can be happily housed in a typical amateur glasshouse provided that it has ample light and ventilation and a minimum winter temperature of around 5 C (40 F). Occasional drops to freezing point will do no harm if the plants are dry. If no heat is available, the choice is much more limited, but not beyond hope. Certain groups of cacti need extra heat. There are the moisture-loving tropical pereskias and Hylocereinae, along with their hybrids, the epicacti....

Dioscoreaceae

The 'Elephant's Foot' (Dioscorea or Testudinaria elephanlipes) is so oddly fascinating that I am tempted to use that overworn cliche a must for every collection. Certainly, if only one caudiciform plant is to be allowed into a collection, this is it. The large, winged seed germinates to produce a 1cm ( in) spherical caudex the first year, with a single heart-shaped green leaf. Slender annual climbing shoots follow, like the black bryony, Tamus. its next-of-kin. As the sphere enlarges it...

Outdoor cultivation in warm countries

Fortunate indeed are those whose climate allows them to grow succulents without the expense of heated glasshouses. This is possible, and widely practised, in southern Europe and the southern USA. in parts of South Africa and Australia, and in the north island of New Zealand. Frosts are not unknown in many of these areas, but are sufficiently slight toallowa wide choice of the more robust succulents to thrive unprotected. Where the summers are hot and dry, as in California, many succulents are...

The Spurge Family

The Euphorbiaceae make up a large and cosmopolitan Family of plants of which the succulent element is but one of many facies. There are estimated to be 300 genera and over 5,000 species, of which one genus. Euphorbia, accounts for two fifths of the species. In the European flora the Family is known only by a handful of small annual or perennial weeds (Euphorbia, the spurges, and Mer-curalis. the dog's mercury, for example). However, most are tropical woody shrubs and trees, including the...

Choosing a container

The act of confining a cactus in a small pot is a radical departure from its normal way of life, where roots spread widely and seek the shelter and moisture of rock crevices. Porous clay pots allow quick drying out and if exposed to prolonged hot sun scorching and death of the fine root tips. Plastic pots are less susceptible to this, but there is the opposite danger of waterlogging in damp, dull weather. Standing porous pots on a bed of shingle, or half plunging them, lessens the danger of...

Commelinaceae

This is a moderate-sized Family of the Monocotyledons comprising about 38 genera and 500 species. It includes Tradescantia. the spiderworts of our gardens, and a number of tender pot plants with foliage decorative for our homes, such as Rhoeo and Zebrina. Succulence is most developed in Tradescantia navicularis from northern Peru, an attractive miniature in which each keel-shaped leaf has the upper surface distended by development of a massive translucent water-storing tissue beneath the...

Crassulaceae

Although this Family (Chapter 10) is predominantly leaf-succulent, three of Below (21 9) Crassula septas in semi-shaded woodland on the slopes of Table Mountain the largest genera also exhibit trends to water storage in stems and roots. Sedum rosea (21.7) has already been referred to on page 116 it is native to the Northern Hemisphere up to the Arctic Circle, and hence the hardiest of succulents, as well as being one of the most variable. In the genus Crassula, the Section Tuberosae includes...

The Century Plant Family

Up to 1934, Agave, the Century Plant', was classified in the Amaryllis Family and Yucca, the 'Adam's Needle', in the Liliaceae. In that year John Hutchinson of Kew realized that there was a strong affinity between the two genera (14.1) and placed them together in a new Family by themselves, the Agavaceae. His decision has been amply supported by later work, notably on the chromosomes and embryology. Yucca includes a number of hardy species and has fibrous, non-succulent leaves it will not be...

Echinopsidinae

Hunt's classification lays stress on the presence of hairs and narrow scales on the outside of the flower tube as distinguishing this subtribe from the preceding, with habit taking second place, so we again have a mixture of columnar and dwarf species, sometimes within one genus. Starting with the tall-growing types, Espostoa, Haageocereus, Cleisto-caclus and Borzicactus (16.15) are worth considering even for a small collection because of the beauty of their stems, with Lett (16.13)...

Crassuloideae

Subfamily I is set apart from the remainder by the single whorl of stamens, equal in number to the sepals, petals and carpels. It is not a primitive character, because it results from suppression of a second whorl, and a reduced pollen output is characteristic of more specialized flowers that can afford to be less wasteful of pollen. A phylogenetic classification of the Crassulaceae, according to Uhl. would look to Sedum as a more likely starting P The 250 to 300 species of Crassula run from...

Names for hybrids

Hybrids, because they occur both in the wild and in gardens, come under both Codes. A hybrid can receive a formula name by combining those of the two parents, thus Echeveria derenbergii X setosa. or, if considered of sufficient importance, a latinized epithet like a species in this case EcheveriaXderosa von Roeder. which includes the author's name at the end. The X preceding the specific epithet is the sign of hybridity. Such a collective epithet covers all descendants from that cross, as well...

Watering when and how much

If any one factor determines success or failure in domesticating wild succulents, it is watering. Many people crave to know the magic formula of how much and when, expecting a simple equation depending on the size of pot, age of plant and maybe the phase of the moon as well. There is no magic formula. Successful growers are those who have come to know their plants, and can tell what to do from the look of them, the feel of the soil and the weather prospects. A stem or tuber just sprouting green...

The pollinators

To the best of my knowledge no succulent is reliant on the wind for pollen transfer (anemophilous), as are the grasses and many catkin-bearing trees and palms. Most depend on the visits of insects (entomophilous) or birds (ornithophilous), although bats (4.6) appear to be the main pollen vector in such nocturnal cacti as the giant saguaro. But we have few accounts of pollinators observed visiting succulents in the wild. Field workers are usually too intent on seeking new species to bother. Who...

Variety of leaf forms

The leaf of a typical mesophyte (2.9) has a thin, flat, expanded green area (the blade or lamina) supported on a stalk (petiole) from whose base on the upper side there is a bud. Additionally, there may be two small lateral outgrowths at the base of the petiole, one on either side (the stipules). The arrangement of leaves on a stem (phyllotaxy) is spiral, or alternate, or opposite in pairs, or sometimes whorled three or more in a ring, as in Peperomia galioides. Gasteria( 13.8) shows the leaves...

The classification of plants

It is basic to the human mind to classify, to break down the things we see around us and file the images for retrieval later when similarsightsappear. The diversity of nature can be interpreted only by some sort of box-within-box storage system. Thus we see the logic behind the hierarchy of categories produced by the taxonomist, as set out in descending order here. This shows the classification for one of the pebble plants, with the status and name of each category. Note that for some...

The Cactus Family

More books are written about cacti than all the other succulents put together, and some add a final injustice by including a chapter on other succulents rather as an afterthought. Indeed, the very word cactus has been taken over by the general public for any fleshy, prickly, bizarre-looking plant a sad distortion of its botanical meaning as a member of the Family Cactaceae. The reasons for the popularity of cacti are not hard to find. First, they all look so different from other plants the...

Passifloraceae

Adenia could be thought of as a poor relative of the passion flowers, Passiflora, having none of the floral splendours of that genus. Of 92 species. 57 are African and a few of these are sufficiently oddly shaped to catch the eye of the succulent addict in search of novelty. Beginning with species where the trunk is extra thick and tapering (A. glauca, A. fruti-cosa) we find a massive more or less cylindrical caudex in A. digitata, spines on the aerial branches in A. spinosa and prickly...

Life forms and survival

Many dwarf perennial succulents a especially adapted to pass the dormant season underground, and are hence to be seen only during the often brief rainy i periods, or when in flower. Indeed some, such as Albuca unifoliata (page 158). ai so retiring that their existence was unsus pected for decades, even in well-worked I areas. Bulbs and caudices are ideally I suited to tide plants over long periods of desiccation.HaworthiaandBulbineafford I examples of plants with contractile roots I that is,...

What chromosomes tell us

Looking at chromosomes under the microscope is, in a way, like looking at the blueprint of life the architect's plan rather than the finished building. This is not the place to enter deeply into the chemical and physical properties of chromosomes a subject that attracts intense interest and research, stimulated by the ever-present desire to learn more about the origin of life. Here it must suffice to give a few simple examples to show how investigation of the number, form and pairing behaviour...

Geraniaceae

Growers of zonal and regal pelargoniums the geraniums of the layman may have little idea of the diversity of this large and versatile genus of over 250 species in the drier parts of South Africa. About the only thing all species have in common is an apparent indifference to neglect and hardships that would kill off anything but a superplant. P. tetragonum is truly stem-succulent, with three- or four-angled, jointed grey-green stems P. echinatum has warty tubercles, and P. gibbosum a gouty...

Caudiciform Succulents

The common feature of plants grouped here is extreme differentiation between temporary food-forming organs (green leaves or shoots) formed during periods favourable for growth, and permanent. non-green, heavily protected water and food stores at or below ground level that enable the plant to endure long periods of desiccation. But the definition cannot be made more precise if one fact emerges from a study of living organisms it is that they cannot be made to fit exactly into man-made...

Succulent Designs

Broadly speaking, there are three types of succulents, according to where the water storage tissue is located in the plant (2.9). Each represents a different life form that is, the overall habit of the plant as determined by its ecological requirements. There is some overlap between the three groups. Leaf succulents are plants with enlarged, fleshy, water-storing leaves, as distinct from those where the bulk of storage is concentrated in stems or roots. Stem succulents are those in which the...

Grafting

The technique for making one plant grow on the roots of another has been known at least since the time of Aristotle, in whose surviving writings we read Grafting of one on another is better in the case of trees which are similar and have the same proportions. Grafting is a useful means of accelerating growth and flowering in slow-growing species, of preserving rot-sensitive rarities and cristates. and of saving a plant that has been all but lost by rot or misadventure (6.24). It consists of...

The chromosome blueprint

To begin at the beginning, we must first look at chromosomes. If we take the tip of a root or stem that is actively dividing, and look at single cells, suitably stained, under a high enough magnification, we can see the chromosomes a constant number of dark, sausage-shaped bodies in each nucleus (5.2). In most cacti, for example, there are 22, 11 derived from one parent and 11 from the other. Each set of 11 chromosomes contains the genes in linear sequence, and by their interaction with the...

General Reading List

Hortus Third Macmillan, New York and London 1976 CHIDAMIAN. CLAUDE Book ol Cacti and Other Succulents Doubledav, New York 1958 GLASS. C. and FOSTER, R Cacti and Succulents lor the Amateur Blandford Press, Poole 1977 Van Nostrand Remhold, New York 1977 GRAF, A. B. Exotica III Scribner. New York 1975. HAAGE, W. Cacti and Succulents Vista Books. London 1963 Dutton. New York 1963. HIGGINS. V. Succulents in Cultivation St. Martins, New York 1960. IVIMEY-COOK. R. B....

Stem Succulents

Tike I In- bramble Some huit no branches, others hire u . real number, like the tyeamwe. Stem succulence implies a greater modification of the plant body than leaf succulence, where the leaves are still the main centres of photosynthesis and the habit may differ little from that of normal plants. In stem succulence the green tissue, and in consequence the vital centre for food-making, is more and more shifted to the stems (2.8) completely so in those plants, such as columnar cacti, where leaves...

Peperomiaceae

As set out by Willis (1973) this Family runs to four genera only, of which Peperomia, with around 1,000 species, is by far the largest (9.2). A relative of pepper, it is centred in tropical South America but extends widely, and many species grow as epiphytes. To our window-sills it contributes some tough, long-lived, leathery-leaved foliage plants, at home in full sun or shade so long as they are kept warm. There is no sharp division between the non-succulent and succulent species all have a...

Natural deception

One evolutionary process of peculiar fascination is that termed mimicry for example, a plant looking so much like a stone that it escapes detection by resemblance to its background. Mimicry is developed to a high degree in the animal kingdom, a colourful example being harmless species of tropical butterflies that escape extermination by developing similar patterns to those of butterflies that are distasteful to their enemies. Mimicry and imitation are bad words to use because they imply a...

Cactaceae

Is TV. nidus, whose crown of interwoven, curling, bristle-like spines is fancifully compared to a bird's nest. The spines can be any shade from white through buff and bright yellow to black, and other hues. A pressing recommendation goes to TV. wagenknechtii (16.26), which begins to open its rings of small but brilliant magenta blooms in October and continues for weeks a fine splash of colour when few other cacti are performing. Typical Neoporteria flowers remain only half open those of...

Cell division

Cells multiply by the process of mitosis. in which each chromosome divides to form two identical daughter chromosomes these separate into two clusters and a cell wall forms between them. In this way each of the millions of cells forming the body of a plant exactly the same set of genes, barring r accidents. a population i. This picture s the tolly ot trying to define a species from a single plant. As a prelude to the development of reproductive cells (gametes), the chromosomes undergo a special...

Cotyledonoideae

The Cotyledonoideae are centred in South Africa but extend northward and, in the genus Umbilicus (3.1), through Ethiopia to Europe and Western Asia. The single species of Chiastophyllum, C. oppositi-folium, a popular hardy rock plant with nodding sprays of pale yellow blooms, comes from the Western Caucasus. Cotyledon (10.8) is really two genera in one, half its 50 species having opposite, persistent leaves and a shrubby habit like Kalanchoe, the other half having spirally arranged deciduous...

Urticaceae

Pilea serpyllacea from Peru is not unlike a Peperomia in habit, but is a member of the unrelated nettle family. Its most noteworthy feature is the pellucid window on the underside of each tiny leaf. It is a delicate plant and likes adequate warmth. Pilea is credited with 400 species, and is the largest genus of the Urticaceae (45 genera, 550 species). Several species of Pilea are in cultivation llnder the name 'Artillery Plant', from the explosive ejection of the anther contents as a cloud of...

Haworthia

Above left (8. t) Adrian Hardy Haworth, (1768-1833 named many new species and is commemorated by the genus Haworthia. although the gravestones , necessary for legibility in botanical gardens are too large tor a private collection. journal offered to the general public. It greatly helps if the author adds illustrations, a description in a second, living language, and indications of how his new species differs from its allies, but none of these is obligatory. Nomenclature is a complicated subject...

Stapelieae

The Tribe Stapelieae consists entirely of stem succulents with thick, often soft and juicy branches covered in low ribs or tubercles, often tipped with a scaly bristle which is all that remains of foliage. A superficial resemblance to cacti is to be found in several. One species from India, Caralluma frerei( 19.6), retains flat, semi-succulent leaves, and is regarded as a pointer to the ancestral prototype from which the Tribe evolved. The main difference from the Ceropegieae is in the form of...

By Gordon Rowley American Consultant Charles Glass 0ver250 Species in Full Colour

Succulents are plants that store water in swollen leaves or stems, enabling them to survive long periods of drought They include some of the most amazing of all forms of plant life, surrealist in form and contour, often spectacular in the beauty of their flowers and bewildering in their ability to survive conditions fatal to most other plants. As house plants for a dry, sunny windowsill, or as cult objects for the connoisseur with a greenhouse or outdoor 'desert' garden, succulents find a...

A little water goes a long way

Succulence by itself would be of little use to plants facing drought conditions without specialadaptations for retaining such water as is collected. Many of the peculiarities of form and structure in succulents can be interpreted in this light. The following list includes a selection of these xeromorphic modifications. Surface reduction. The surface of a succulent may be reduced to as little as Vjog of that of a comparable mesophyte. Leaves are the first to go. or at best are simple in outline...

How succulents evolved

The story of the evolution of plant life on this planet is the story of the conquest of dry land. From microscopic beginnings beneath the sea, of which the seaweeds (algae) are modern survivors, plants evolved the means to become independent of a continuous water supply for at least part of their life cycle, and were thus able to colonize the land. Mosses and ferns are still usually plants of moist shady places conifers show a marked advance, as well as possession of a woody skeleton. Finally...

The Periwinkle Family

A predominantly tropical Family, the Apocynaceae comprise about 180 genera and 1,500 species. They are mostly twining plants with a white milky sap (latex). The flowers are often quite showy and some genera (such as Allomando) are grown as glasshouse climbers. The shrubby Plumer a is the 'Frangipani', grown throughout the tropics for its scented blooms. Some growers of succulents have stretched the limits of their collections to include it on the strength of slightly fleshy branches. Vinca, the...

Echinocactinae

Lophophora Yellow

All 20 genera of this subtribe are esteemed by cactophiles, and the majority are solitary or form compact mounds of heads, and accommodate well to small . pots in a glasshouse. Taking the largest-growing first. Echinocactus (6.11) and Ferocaclus (2.1. 16.29) are the barrel cacti, conspicuous features of the drier areas of Mexico and the southwest USA. But even though potted specimens need to be large before flowering, the plants are valued for the superb spines, often hooked in Ferocaclus and...

Breeding new succulents

Every plant does not produce a seed similar to that from which it is sprung some produce a better seed, others a worse. This quote from the same ancient source that provides the chapter headings used here may be taken as the birth certificate of plant breeding. A hybridist can achieve in one lifetime what might take millennia if left to nature. He can speed up evolution, bringing togetherand crossing plants from widely separated localities, and can even open up quite new sources of variability...

Dispersal

The second function of flowers, following cross-pollination and fertilization, is the dissemination of seed. Efficient dispersal requires that daughter plants grow up sufficiently far from the parent to avoid direct competition, but not so faraway as to lessen chances of cross-pollination. Long-distance dispersal provides the means of founding new populations and increasing the range of a species. Dispersal mechanisms have been classified under five groupings6 wind, water, mechanical means,...

Attracting the pollinators

Sprengel, a rector in Spandau in the late I eighteenth century, was the first to study I the devices whereby flowers attract potential pollinators. He noticed the baits I offered surplus pollen and nectar. He I observed the form and design of the I flower, and the way contrasted areas of colour nectarguides pointed the way to the source of food. Such guide lines in red I can be seen on the petals of Pelargonium I fulgidum 4.5 . Some visitors bats, for instance eat not only pollen but whole I...

The Didierea Family

This distinctive and isolated Family, endemic to southwest Madagascar, makes up for its small size by many features of botanical interest. Like the Cactaceae. to which it runs parallel in many ways, for a long time it resisted efforts to fit it into any system of classification, seeming to have no close allies. Now, however, anatomical features and the possession of the pigment beta-cyanin have sited it in Caryophyllales next to the Cactaceae, with which successful grafts have been made an...

A cactophiles progress

Overall, the grower of succulents has fewer worries from pests than the cultivators of many other flowers and vegetables. It has been said with some truth that a cactophile spends the first half of his life trying to make his plants grow, and the second half trying to stop them. Overcrowding soon becomes a problem, no matter how large one's glasshouse, especially if seed is raised. Although one can go on adding shelves and hanging baskets, there comes a point when the plants are no longer...

References

References relating lo Chapters 1-8 arearranged t BAUHIN. J and CHERLER - Hisloria Plantarum Generalis Prodromus Yverdon 1619. 2. BRADLEY, R - The History of Succulent Plants London 1716-27. 3. BROWN, B. N. E. in The Gardeners' Chronicle Feb. 12, 1927 116 and Apr. 9,1927 251. 4 HEYNE. B. in Transactions olthe Linnean Society 1814 213-15. 5. JAMES. W. O. in Endeavour XVII 90-95, 1958. 6. TATE, J. L. Cactus Cook Book Cactus amp Succulent Society ot America, California 1971. 1. SPALDING, E. S. in...

The Purslane Family

Succulent Plant With Dried Stipule

This is another Family of the Order Caryophyllales. and all its members are more or less succulent. However, many are small-flowered annuals and of interest only to the botanist. Of the 19 genera, about seven are represented in succulent collections. All are leaf succulents. although with a frequent tendency to the caudiciform in Anacampseros A. alstonii, 21.22 . Talinum T. caffrum. T. guadalupense. 15.4 and some Portu-lacas. The leaves are always entire and often bear at the base long white...

Sedoideae

Lampranthus Conspicuus

Sedum, with 600 species, is the largest genus of the Family and the least well-defined, most of the other Sedoideae being splits or at one time or another included within it. It covers the North Temperate regions, with outliers extending south to Peru, Central Africa and Madagascar. and occupies an equally wide range of habitats including a few species in marshes S. villosum and some epiphytes S. epidendrum . Some of the hardy species are herbaceous perennials, with leafy shoots that die down...

Euphorbieae

Like the Compositae, the Euphorbieae have evolved an inflorescence that looks and functions like a single flower. Let us take a close look at one of the most familiar the 'Crown of Thorns', Euphorbia milii splendens 20.6 . The two red organs are not petals but coloured bracts, and each bears in its axil a dormant bud that can later grow out and add a new branch to the inflorescence. In the centre we find a single female flower reduced to THE SPURGE FAMILY EUPHORBIACEAE A breakdown to genus...

Vegetative propagation

Although the only practicable way to propagate a few succulents Ariocarpus, Astrophytum, Frithia. Euphorbia obesa . is from seed, most lend themselves more or less readily to vegetative multiplication by division 6.20 . offsets, suckers, cuttings 6.21 , adventitious buds or grafting. Having their own internal water store, they suffer less than most plants from the temporary interruption to water intake. Vegetatively propagated plants have a head start over seedlings, and are Tap the plant out...

Hylocereinae

Here we come upon plants more typical of tropical forest regions than semi-deserts, and adapted for life as epiphytes or lithophytes. The stems are typically long and flexible many metres in some and, except in Aporocactus. have few Right 16.19 Lobivia densispina flowering in a 6 cm 2Viin pot Like Rebutia. Lobivia is a good genus lor beginners and flowers freely on small specimens. Below 16.20 Rebutias set seed readily in captivity but Ihe seed is olten hybrid For pure seed, hand-pollination of...

Portulacaceae

Chapter 12 covers the leaf-succulent members of this Family and Chapter 15 those with fleshy stems. There are also a few species of Portulaca and Talinum 21.21 with swollen underground storage organs and more or less deciduous aerial parts. Talinum caffrum is noteworthy for its pleasant yellow flowers like small primroses, and grows rapidly from seed. But the greatest treasure, and quite unique among succulents, is Ana-campseros alstonii 21.22 , with a flat cake-like caudex up to 10cm 4in or...

Patterns of distribution

To portray such a range of concentrations would require an enormous map and many fine shades of colouring, and to the best of my knowledge nobody has yet attempted one. If there were such a map. the heaviest shading would come around the horse latitudes. 30 N. and 30 S. of the Equator, and it is certain that South Africa and subtropical North and South America would score highest for numbers of speciesas well as for density of populations. America is the home of the cactus Family Cactaceae and...