To locate the end of Charles's evolutionary period and the beginning of his physiological period as occurring precisely in 1860, as Francis did, suggests that a sudden change overtook his father. No such abrupt change happened, of course, although Francis's essential message was nevertheless valid; a watershed had occurred in 1860 marking a fundamental change in his father's focus and method of working. There was, in reality, a slow and lengthy period of transition, full of hiccups. Throughout the 1860s and ’70s, Charles switched the focus of his attention from one group of plants to another, and then sometimes back again (see Table 6.1, overleaf). Projects overlapped with one another. First he would be concerned with insectivorous plants, next with orchids, then again with insectivorous plants – with attention to climbing plants being fitted in between. Capable of a seemingly obsessive interest in one group, he had an astonishing ability to keep several other interests ticking-over in the background. Whether it was by observation of the plants in his garden or greenhouse, or those in the countryside around Downe, he was always watching and noting what was happening to plants, often tinkering with them in ways that would one day lead to major investigations. Prize plants, sent by Hooker or some other botanical correspondent, were often kept on the windowsill in his study where he could watch them day by day, or even hour by hour, making notes that might be useful at some time in the future.

From his studies of climbing plants and of insectivorous plants he learned new facts about convergent evolution and about competition, facts that complemented his evolutionary studies, providing additional material for his regular revisions of On the Origin of Species. Little by little, however, his viewpoint changed. He became more and more aware of questions about possible links between structure and function. His observations of the circular movements of the shoot apices of climbing plants, for example, or the rapid movements of the sticky tentacles and snapping leaflets of insectivorous plants, led him to contemplate the physiology of the plant.