The study of traditional medicinal herbs is an important element in the science of Ethnobotany. Over many hundreds of generations, local people in various areas learned which plants could be used to treat or prevent various illnesses. Much of this knowledge was gained painstakingly, through long years of experimentation. The knowledge was then passed down, often through a line of shamans or other traditional healers.

Japan is rich in medicinal herbs. Gathering data on their traditional uses, however, is surprisingly hard. One reason for this is that kanpo, a formal system of herbal medicine developed in China, was imported to Japan more than 1,000 years ago. As kanpo medicines became widely available, they often replaced traditional remedies. In addition, after the Meiji Restoration of 1867, the Japanese government actively promoted the spread of Western chemical medicines, and in many regions the traditional medicinal plants were forgotten.

But several traditional medicinal plants are still widely remembered and sometimes even harvested and used locally. One of the best-known of these is the Thunberg's cranesbill, a neat little geranium with white or pinkish-white flowers (in some areas the flowers may be a deeper pink) that bloom from late summer through mid-autumn.

At this time of year, the cranesbill flowers are finished, but the fruits are getting ready to put on a most interesting and rewarding display. All plants try to disperse their seeds as far away from parent as possible. Some species, like dandelions, utilize the wind, while others get their seeds carried away in the pellets and scats of birds, or stuck to the hairs of passing animals. The cranesbill, however, sends its seeds flying with a catapult that, ounce for ounce, easily outperforms any mechanical device invented by humans.

The cranesbill flower has a single pistil that is divided into five sections at the tip. Once pollinated, the pistil grows into a long, thin beaklike structure that gives these plants their common English name. A close look shows that the beak is divided into five long slatlike segments, each with a round, hairy pouch at its base. These pouches contain one seed each.

As the weather grows cold and dry in late autumn and early winter, the slat segments begin to tighten up and pull away from each other and the central pole around which they are attached. They continue to dry and tighten until they tense up like little leaf-springs just itching to be released. At the same time, the pouches also begin to split open along their seams. Then one cold, dry day, the slats suddenly spring free at the base, and snap upward in a tight curl. The momentum of this snap hurls the seeds right out of their pouches and sends them flying across the countryside.

The cranesbill's slats are only about a centimeter long, and the seeds about a millimeter in diameter. Still, some plants manage to hurl these seeds over awesome distances. One American botanist set up some cranesbills inside a cloth tent to measure how far the seeds flew. The results showed that some of the best shots covered a distance of close to 10 meters.

Cranesbills (genus Geranium) are found throughout the temperate zone, and are familiar plants in Europe and North America. The American species (G. maculatum) was widely used as a medicinal herb by both natives and early settlers, not only to treat stomach disorders but also as a styptic for open wounds. In Europe, Herb Robert (G. robertianum) was a traditional remedy for various stomach ailments.

Japan is home to about a dozen species, but the Thunberg's (G. thunbergii) is by far and away the most common and also the best known as a medicinal herb. People throughout the country consider it dependable and fast-working. In fact, the Japanese name for this plant, gennoshoko, means something like "the effectiveness soon appears."

In Japanese folk medicine, the cranesbill has been used mostly to treat mild diarrhea, which until quite recently was an extremely common ailment, especially among children. The active ingredients, which include tannins, are found in the entire plant, but are concentrated in the leaves, which are cut and dried and then decocted to make a thick drink.

In the area of northern Chiba where I work, every farmhouse used to keep a supply of dried leaves on hand. Over the past several decades, however, improvements in sanitation and food processing have drastically reduced the incidence of diarrhea, and only elderly people still collect and prepare cranesbill leaves. This species, however, is formally recognized as a medicinal herb under the Japanese Pharmaceutical Law, and standardized dried leaves can be purchased by the bag at any well-stocked drugstore.

Look for the Thunberg's cranesbill on sunny roadsides, woodland meadows, at the edge of forests, and along the aze dikes that separate the rice paddies. The leaves that arise from the base of the plant are about the size of a 500 yen coin, and are usually cut into five sections. The leaves on the flower stalk are smaller and simpler. The beaked fruits will be in twos at the tips of the stalks. Some will have already launched their ammo, and will look like a tiny merry-go-round or maypole. A favorite Japanese nickname, mikoshigusa, refers to the appearance of the spent capsules, which remind people of the fancy gabled roof of the portable mikoshi shrines used during Shinto festivals (kusa or the combined form gusa is a generic term for an herbaceous plant).

(From The Yomiuri Shimbun)