Photo by John Nelson Paris?

Yes, I was just there a few weeks ago. Sure, you can go to the Eiffel Tower and see all the big draws, but when you go, what you really need to do is figure out a way to blend in, and make it special. See the Seine at dawn or at midnight. Play chess, launch a toy sailboat, or ride a donkey at the Jardin de Luxembourg. Get lost in the Marais, or visit a street market on the Left Bank and buy enough goodies for a picnic at any one of the many beautiful parks. Eat some snails or brains (remember Andy and Barney at the French restaurant in Raleigh?), and take lots of pictures.

So what did I photograph? Nuts on the sidewalk.

These spiny things fall out of trees that are widely planted in Paris but also throughout the rest of Europe. This tree is native to western Asia and is widely grown as an ornamental all over the northern hemisphere. It makes a marvelous shade tree and is thus grown as a popular street tree and also in beer gardens. It likes things a bit cool, so you don't usually see it in the USA any farther south than about New England. It can be a large tree with smoothish, gray bark. The leaves are opposite, two at a time on the stem, and each is palmately compound with five prominent, toothy leaflets. It makes plenty of flowers in the summer time, each one with five white petals, and there are several dozen clustered together in a panicle.

Now, the spiny things are actually the outer walls of the fruit. Each fruit will release two or three seeds which are smooth-skinned, shiny, and reddish brown. A prominent scar from the fruit wall remains on each seed. Historically, the seeds have been used medicinally and sometimes carried in a pocket as a good-luck charm.

Generally, though, and in this tiresome modern age, the fruits and seeds are something of a nuisance and on the streets just swept up and discarded. These seeds look very similar to the true, culinary "chestnuts" (or "castanies") which are often offered in Europe on the streets as a winter treat, roasted. Be aware, though, that the seeds of our Mystery Plant are pretty much inedible. These are never offered as a snack.

There are several relatives of this plant, naturally occurring, here in America, one of which, in the Southeast, is actually quite rare along the Savannah River. Ohio State fans pay certain homage to a Midwestern U.S. species whose fruit wall is smooth, lacking the spines. Its seeds are likened to the eyes of a certain animal that runs around in the woods here and there and in the highways, and for whatever reason, OSU fans find good fortune in their eyes.

Answer to this week's mystery plant

Horse chestnu, Aesculus hippocastanum

Dr. John Nelson is the curator of the USC Herbarium.

To learn more about the Herbarium, call 777-8196. The

department also offers free plant identification.

www.herbarium.org