Evolution has for a century and a half been the subject of both speculation and research. It has been approached from almost every imaginable side. However, while on the one hand the fossil evidence has provided us with the main lines of development both of characters and of taxa, and on the other comparison of living organisms mutually and experiments of various kinds have given us some insight into the processes which may play a part in the mechanism of evolutionary development, the two methods of research are still separated by a wide gap and in spite of many efforts we are far from understanding what is really happening and what the admittedly necessary connection between the framework and the skin may be. In a recently published book the Swiss artist-botanist Erich Nelson has offered a contribution to the static (or short-time) side of the problem. It must be admitted that his considerations are bearing on a part of the field only (viz. Angiosperm flowers) and that an ample, though by no means exclusive use is made of facts which were already known, this does not lessen the merit of the author that he has contrived to open up a new and promising field of research by expounding a rather bold but consistently argumented theory which seems well worth considering.