"Taxonomy: Evolution at Work" unfolds as a story explaining the strategies in which the different plant groups evolved over time and their struggle for survival by developing new and better characters.
The problems faced by the primitive group of land plants are explained and the methods by which the plants intelligently outwitted the adversaries such as insects, herbivores, parasites etc. or adverse environmental situations are described. The adaptations thus achieved by the plants made them an evolved taxon.
The plants of this taxon, in turn, when faced by new unfavorable situations, elaborated still better characters and formed a third taxon.
Similarly fourth, fifth and the n'th taxa evolved. All plant groups are described in terms of their successful adaptational characters (intelligence!) and the study of these processes is the study of "evolution at work" and this is precisely the subject of taxonomy.