[Note: This is an excerpt from The Ancestor's Tale, Rendezvous 36 (Plants), pp. 509-510. Dawkins explains a program called Deep Green (which I, too, highly recommend).]
In the case of the green plants, I strongly recommend a stunningly well-produced computer program called Deep Green, which, at the time of writing, is available on the internet. When you launch Deep Green, you see a rooted phylogenetic tree. Some of the branches have a name at the tip, the name of a plant or a group of plants. Some of them have no name and are pointing 'off the page'. The beauty of this program is that you may seize the tree with your mouse, and drag it, in the most delightfully natural and intuitive way, to see more of the tree. As you drag, you watch twigs sprout before your eyes, and as you swivel the tree round, you see a whole lot of new names appear on the screen, together with many new, unnamed branches. You then explore the tree as far as you like: it seems to go on forever, which tells you what a huge diversity of green plants has evolved. As you climb through the branches, hand over hand as it seems, like a Darwinian monkey in evolutionary tree heaven, remember that each fork you encounter represents a true rendezvous point in exactly the sense of this book. It would be wonderful to have an animal version, too.