"Imagination and shrewd guesswork are powerful instruments for acquiring scientific knowledge . . . " 1. H. van't Hoff The last decades have witnessed a rapid growth of quantum chemistry and a tremendous increase in the number of very accurate ab initio calculations of the electronic structure of molecules yielding results of admirable accuracy. This dramatic progress has opened a new stage in the quantum mechanical description of matter at the molecular level. In the first place, highly accurate results provide severe tests of the quantum mecha nics. Secondly, modern quantitative...

What are plant growth regulators? In the title, and throughout the text, we have adopted this expression to describe a population of endogenous molecules and synthetic compounds of similar structure that are be- lieved to play important roles in the regulation of plant differentiation and development. For many years, plant scientists have endeavoured to understand the nature and action of plant growth regulators and, as a result, an awesome quantity of written material now exists describing these chemicals and their effects. In this book we have aimed to distil this wealth of information into...

The last few years have seen a number of new books on evolutionary biology. However most of these are either large or specialized. This is an attempt to produce a thin, general version for undergraduate use. Thinness, of course, demands selectivity, and the aim has been to concentrate on the principles of the subject rather than on the details-principles, that is, of both theory and practice. Thinness also sometimes means that a certain level of knowledge is assumed in the readership, but I hope that this is not the case here, and my intention has certainly been to produce something that is...