Philosophers through the ages have made the astute observation that life, in its many aspects, appears to be continuously moving. All things in the universe, from the cosmic to the atomic level, exhibit some form of movement. Getting down to earth, the capacity to move is also an essential feature of the biological world. Movement was in fact synonymous with life at the time that Antony van Leeuwenhoek made the first simple microscope (seventeenth century). Using his primitive instrument he observed micro-organisms. which he called 'animalcules', swimming through a drop of water, and...

Vegetation dynamics is an important subject. A knowledge and under- standing of it is central to the science of vegetation management-in grassland, range and nature reserve management, and in aspects of wildlife management, forestry and agricultural crop production. It is also a large and diffuse subject. In a small book such as this I had to be highly selective, and could not do equal justice to all aspects. I have had therefore to condense many examples, and more regrettably, many arguments. While I have tried to present a broad selection of topics and examples, the content inevitably...

This book is about the regeneration of plants from seed under field conditions. It attempts to give a reasonably balanced overview of the many aspects of this broad topic. The first chapter introduces some general ideas about reproduction in plants. Subsequent chapters deal with the early stages in the life of a plant, from ovule to established seedling, in a more or less chronological order. The final chapter shows how the data on regeneration requirements of different species can be used to explain a number of important characteristics of whole plant communities. The study of the ecological...

The student of biological science in his final years as an undergraduate and his first years as a graduate is expected to gain some familiarity with current research at the frontiers of his discipline. New research work is published in a perplexing diversity of publications and is inevitably concerned with the minutiae of the subject. The sheer number of research journals and papers also causes confusion and difficulties of assimilation. Review articles usually presuppose a back- ground knowledge of the field and are inevitably rather restricted in scope. There is thus a need for short but...

viii homology groups. A weaker result, sufficient nevertheless for our purposes, is proved in Chapter 5, where the reader will also find some discussion of the need for a more powerful in- variance theorem and a summary of the proof of such a theorem. Secondly the emphasis in this book is on low-dimensional examples the graphs and surfaces of the title since it is there that geometrical intuition has its roots. The goal of the book is the investigation in Chapter 9 of the properties of graphs in surfaces; some of the problems studied there are mentioned briefly in the Introduction, which...