The commanding position to which these men attained in the world of science was of course due, primarily, to their ability and--equally of course--to circumstance. The great wars were over and in the peaceful years men were free to turn their energy to constructive purposes. Horticulture--ever a British art--became unreservedly popular. Explorers and collectors, encouraged and assisted by Banks and others, sent home rich supplies of new or rare plants and thus provided British systematists with a vast array of material for their work of reconstructing the flora of the world. Such brilliant use was made of opportunity that our country took the lead in systematic botany. The activity of the collector, the generosity of the patron and the labour of the systematist led not only to a general advance in methods of classification but also to a very special advance in the knowledge of what is, in many ways, the most interesting group of plants on the face of the earth--the Orchidaceae. Among the plant-treasure from India, Australia and Malaya were large numbers of epiphytic orchids. The problem of cultivating such strange and fascinating plants challenged the skill of the gardener. The "fancying" instinct, latent in every Englishman and curiously characteristic of the race, was evoked by the bizarre form of these plants. Orchid-growing became the hobby of the well-to-do. Gardeners with no knowledge of science and regardless of text-book dicta on sterility, proceeded to raise the most marvellous series of hybrids--bi-generic, tri-generic, multi-generic--which any sane and scholastic botanist would have declared to be impossible. Brown, Blume and above all Lindley threw themselves with enthusiasm into the task of discovering the clues to the classification of these plants, the form of whose flowers transgress so glaringly the rules of morphology--dimly surmising perhaps that if the key to evolution is ever to be found it will be discovered by the study of the group of plants which appear to represent evolution's latest prank.