The Cactus Handbook (Der Kakteen Führer), Erik Haustein, translated by Pamela Marwood (Cathay Books 1988)
This book reminds me of the Philip’s Guide to Seashells, because it carries the same important themes: cacti can look very different, but they descend from a single common ancestor and their shape and color are governed by evolutionary changes in a few relatively simple variables.
But there is one big difference between shells and cacti: the shells are dead and don’t change any more; the cacti are living and do. That means that there can be a startling contrast between the vicious spikes or blistering hairs of a cactus, intended to permanently deter, and its beautiful flowers, intended to periodically attract. Notocactus ottonis, for example, is a ridged ball of tough green flesh set with dozens of spikes; its flowers are a beautiful little fountain of yellow petals. Parodia sanguiniflora has even more spikes and even more beautiful flowers: a spray of scarlet petals around a golden heart of anthers and stigma. If the book was scratch’n’sniff, the contrast would because even sharper, because the flowers often smell attractive too.
All of that is adventitious from the human point of view, because the flowers and scent aren’t intended to attract us. But they do, and so do the strangeness and toughness of cacti, which is why a German author has written a highly detailed guide to plants from South and Central America. Some could probably never be grown in Germany, being far too large and demanding even for a specialist greenhouse; others can be grown anywhere with simple equipment.
And once again, as with any sufficiently detailed book about plants or animals, the scientific names have an appeal of their own: Mitrocereus fulviceps isn’t properly illustrated and perhaps could never live up to its name, which means something like “wax-cap tawny-head”, while the name Gymnocalycium horridospinum combines beauty and threat in the way the plant itself does. Its spines are indeed “horrid”, but beautiful violet-pink flowers sprout between them.
The cone-shells provide a similar contrast between beauty and deadliness, but you don’t actually see the deadliness of a cone-shell. However, you need a specialist vocabulary to describe both cone-shells and cacti properly, and both these books will help you acquire one. Being dilettantish, I haven’t put the effort in, but I know I should do, because it would help me to a deeper and richer appreciation of what I’m looking at.