Another one of my cacti is in bloom. I couldn't identify the species of the first one that bloomed earlier this year, but I do know the species of this one. It is a Mammillaria hahniana, also known as the "Old Lady Cactus," distinguished by its white hair. These cacti are common in cactus gardens, and this one has bloomed before during its tenure in my collection. I put this plant out on the terrace with the other cacti and succulents and it had a good summer of sunlight and desert-equivalent conditions, so it was lively enough to flower once I brought it inside. The buds appeared some weeks ago as a ring of white fuzzy cones around the top, and when ready, the flowers emerged one by one, though not in a complete ring the way it did the last time it bloomed. Here are two pictures of my hahniana cactus, one in cloudy light and one in sunlight.

You may also notice, although this isn't entirely clear in the photograph, that the areoles, the cone-shaped points on the surface of the cactus from whose apexes the spines emerge, form neat spiraling lines that move in towards the center of the top of the cactus, which is where new growth forms. This spiral structure of cactus areoles forms what is called a Fibonacci spiral, after the mathematical series discovered by the twelfth century Italian mathematician Leonardo Fibonacci. The Fibonacci series, in which the next number is the sum of the two previous numbers, has been found to describe all sorts of growth processes, especially in living things. The series, when translated into a series of squares of proportional sizes, generates the Fibonacci spiral, which can be seen in flower heads, seed pods, pinecones, the famous chambered nautilus shell (seen on the Fibonacci spiral webpage) and the areolae of my hahniana cactus.

Why should this spiral appear so often in nature? Why not other spirals? The science writer Michael S. Schneider has written a wonderful if somewhat New Agey book, called "A Beginner's Guide to Constructing the Universe," in which he talks about why the world we see follows mathematical rules and the patterns generated by the first nine integers. In chapter five, on "fives" in nature, Schneider explores the Fibonacci series and spiral. The spiral appears in growth patterns, he explains, because:

….Although different in size, every segment (of the Fibonacci spiral) has the same curvature. If a microphotograph into the eye (of the spiral) were enlarged, it would find another part of the spiral upon which it would fit exactly. No other spiral will do this, nor will any other spiral accommodate the dynamic balance that nature values.….These characteristics are the open secret of balance of animal horns, seashells, plants, and galaxies.….the tree that puts out branches and leaves in spiral "staircases" around their respective "eyes" can get enormously large; yet the tree always balances no matter how massive it grows to be." (Schneider, pg. 148-149)

This also holds true for my little cactus. As the new growth and new areolae appear at the top, they expand proportionally at the same curvature, forming a concentric cluster of Fibonacci spirals at the top. To see what kind of wild, psychedelic images computers can generate from Fibonacci spirals, visit this site, maintained by artist Edward S. May. But somehow, I prefer to look at my non-computer-generated, hairy, spiny cactus with its little magenta flowers.

Posted at 3:52 am | link