Bridging the gap between scientific texts and everyday horticultural books, this guide provides an insight into the relationships between garden plants and their environments, the history of plant development (as studied through fossils), and DNA studies, set to revolutionize classification.
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Roger Phillips pioneered the use of colour photography to reliably identify natural history subjects. He has 30 books to his credit and has won numerous awards, including three for the best designed books. He wrote and presented two major television series: BBC's Quest for the Rose and C4's 3000 Mile Garden. Martyn Rix is a botanist, plant collector and gardener. He has produced 17 books and numerous scientific papers and collaborated with Roger Phillips to producing 23 illustrated titles for the Pan/Macmillan gardening series. He was recently awarded the Gold Veitch Memorial Medal by the Royal Horticultural Society for his services to horticulture.Excerpt. © Reprinted by permission. All rights reserved.:
The Botanical Garden Volume I: Trees and Shrubs
Our aim in this book is to provide new information and a new way of looking at plants and gardening from a more botanical viewpoint. The plant families are covered systematically, and the relationships between them are discussed; readers will be able to put the knowledge they have acquired piecemeal into a framework, and understand the botanical groups and the similarities and differences between them.
Genera and plant evolution
This book is based on the genus, genera in the plural, the Latin word for family, class, or race. Plants are classified in a hierarchy of many ranks, but the only three commonly used are family, genus, and species. To take an example, the black or water birch Betula nigra is a species in the genus Betula and the family Betulaceae. A genus is usually a very natural and familiar grouping, such as oak, beech, day-lily, or dahlia. Many genera are small and easily recognised by a combination of characteristics not found in another group of plants, for instance the green flowers, lobed leaves, and dry, winged seeds of Liriodendron, the tulip tree. Other genera are large, with tens or even hundreds of species, and can be further divided into subgenera; some botanists may consider these subgenera worthy of division into distinct genera, for example the division of Cornus into Benthamidia, Chamaepericlymenum, and Swida. Modern studies sometimes confirm these divisions, or sometimes show them to be artificial. The plant world can be imagined as a huge, chaotic, and multi-stemmed tree, branching repeatedly, with some branches dying, others thriving and waxing or waning in importance through the millenia. Some branches have survived almost unchanged for millions of years, others that were formerly very important have died out. A few have left just one or two remnants as isolated individuals on remote islands, in gorges, or in mountain forests; others have prospered and now exist as thousands of species.
The classical arrangement
Botanists are faced with the problem of showing in a list this complex result of millions of years of different lines of evolution. Linnaeus' system was based strictly on the sexual parts of the plant, the number of styles and stamens in each flower. This was convenient and worked quite well, but it was clearly artificial. Botanists soon began to work on more natural systems reflecting the evolutionary ancestry of plants, and ever since have continued the search for more natural groupings. The classical order of families was based on the premise that evolution of flowers was from the simple to the complex; thus magnolia and its relatives, with large, simple flowers, were considered especially primitive; daisies, on the other hand, with many flowers aggregated into a head that looks like a single flower, were considered advanced.
To classify modern plants accurately, we need to know their ancestry. Plant remains fossilize very poorly compared with bones or shells, but we can guess from fossils that trees in the coal-forming forests might have resembled giant clubmosses, horsetails, ferns, and conifers. Our knowledge of early flowering plants, probably appearing in the Jurassic, is even more scanty; it is likely many were aquatic herbs with no woody parts. Fortunately, we now have a new tool, DNA, to give clues to ancient relationships. DNA studies have confirmed the classical outline, but also show the true picture to be more complex. The relationships of several groups of plants that did not fit conveniently into any of the old schemes are now being clarified. Some of the major groupings and new evidence concerning their ordering are outlined on the following pages. Volume I follows broadly the order and relationships proposed by Kubitski and adapted by Mabberley in The Plant Book (1997); in Volume 2, I have been able to take into account more recently published DNA studies and have broadly followed the order proposed by Judd and co-workers in 1999. The monocotyledons are placed at the end in both volumes.
Tree ferns, ginkgo, and conifers
The ancient tropical swamp forests, which have ended up as coal today, were dominated by giant clubmosses, seed-ferns, and tree ferns, with primitive conifers. Few remnants of this flora have survived, probably because of the drastic changes in the world climate between the warm, wet Carboniferous and the dry Permian periods. Only some ancestors of Osmunda and relatives of the huge tropical fern Marattia survived from these warm forests; the modern ferns are a result of active evolution and divergence during the Triassic and Jurassic. Most of the tree ferns (see pp.16-17) are found in wet, cool tropical and subtropical forests, and the hardier ones come from the southern hemisphere. Ginkgo biloba (see p.18) is a remarkable survivor, the only one of its family. The leaves of this species and of many other, now extinct, Ginkgo species are found as far back as the Jurassic, and throughout the northern hemisphere in the early Tertiary. A second species, G. adiantoides, survived until the Miocene in North America, and into the Pliocene in Europe. Ginkgo biloba survived somewhere in China, where it was recognised as something special by early Chinese civilisation and widely planted in temple gardens. Other relicts such as the conifers Metasequoia glyptostroboides (see p.38) in China, and Wollemia nobilis in Australia also show how an ancient genus can survive in a small remote area. Conifers are today by far the most important group of ancient woody plants; they are thought to have originated as far back as the Devonian, but most of the present-day families can be traced back only as far as the Jurassic or Triassic.
Magnolia, bay, and Calycanthus
This group of families is interesting in having various combinations of primitive characteristics, that is, features that may have been present in the earliest flowering trees to grow on earth. Primitive wood anatomy, aromatic leaves, spirally arranged floral parts, and simple stamens with undifferentiated filaments are characteristics common in the group and thought to be primitive. In Magnolia, Michelia, and Liriodendron (the Magnoliaceae, see pp.56-59), the flowers are large and often showy, with numerous spirally arranged petals, stamens, and ovules. The related family Annonaceae (see p.65) is mainly tropical, and contains the custard apple, Annona, and the North American pawpaw, Asimina triloba. Winteraceae (see pp.60-61) which includes Drimys, is also primitive in many characteristics and probably belongs with the magnolia group. Also related to the Magnollaceae are the small but interesting families Illiclaceae (see p.63) and Schisandraceae (see p.62); Schisandra, with its unusual red, fleshy fruits in hanging chains, and Kadsura, with similar fruits in a round head, are the only genera in the latter. The bay tree family, the Lauraceae (see pp.66-71), contains over 2500 species, mainly in the tropical forests. Most species have small flowers but sometimes large fruit, for example the avocado tree Persea americans. Others are aromatic, including the bay itself, Laurus, and Cinnamomum, the cinnamon. Related to Lauraceae is the Calycanthaceae (see pp.72-73), containing both the chocolate-brown flowered Carolina and California allspice, Calycanthus, and the lovely white-flowered Sinocalycanthus, recently discovered in China.
Witch hazel and Liquidambar
The witch hazel family, Hamamelidaceae (see pp.99-109), and the related Cercidiphyllaceae (see p.96) are superficially similar in many characteristics to the catkin-bearing plants such as hazels (Betulaceae, see below and p.119). Hamamelis itself has clusters of strongly scented flowers with ribbon-shaped petals; in Corylopsi
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Descrizione libro Macmillan, 2002. Hardcover. Condizione libro: New. Never used!. Codice libro della libreria P110333748905