It is the essence of a living language like English that words pass in and out of fashion. New words are invented (nowadays mostly by computer geeks and people in California) and old terms and expressions that once were useful disappear. Mention the word "mast," for example, and most people will think you are referring to the pole that holds up the sails on a ship. But a couple of generations ago, mast had another meaning. It came from an ancient Germanic word that meant "meat," and it was handed down through Old English as a term for the crop of nuts that fall to the ground and are available as food to animals. A reminder of the old Germanic root is found in the vocabulary of my generation even today; we older folk still refer to the edible part inside the shell as the meat of a nut.

Botanists classify nuts as a type of fruit. Technically, the nut is the hard shell, which we usually discard; the edible part, which we mistakenly call the nut, is actually a seed. This seed consists of two parts: an embryo, which will grow into a new tree, and a food supply for the embryo to live on until it can make its own food. When we eat a "nut," in effect we are stealing that supply of food.

The food reserve in the seed is a rich source of energy, and animals of various kinds have come to depend on eating nuts as their means of survival in wintertime. This has been a dilemma for trees ever since they appeared on earth. On one hand, the best way to ensure that a seed will germinate successfully is to bury it in the ground, and animals such as squirrels, other rodents and some birds do that when they hide their winter stashes. On the other hand, if these animals eat all of their hidden supplies, there will be none left to germinate.

Fortunately, because they have such a long life span, trees do not have to reproduce successfully every year in order to perpetuate their species; and therein lies the solution to their dilemma. As a survival mechanism, they have developed a pattern of producing "normal" crops of nuts in most years, while they store food reserves in their roots. The populations of nut-eaters will adjust to this "normal" food supply. Then, when a year with good growing conditions comes along, the trees will mobilize their stored reserves and produce an extraordinary crop of nuts… more than the animals can possibly consume. Thus, every few years, it is inevitable that some of the hidden nuts will not be eaten, and a new generation of trees will be ensured. Ecologists call these special times "mast years."

Mast years are among my earliest memories. There was a big hickory tree in our yard, and at age 3 or 4 I discovered that the shells would float. A quarter of a shell made a very fine canoe, and I spent hours imagining I was Hiawatha and floating it in the catch-basin of the pump at my grandmother's well. One year there was an extraordinary crop of nuts, and I had enough canoes for battles between Indian tribes. That year we also had a glut of walnuts, which we gathered in burlap bags and dumped in front of the garage, where the car would run over them and remove the outer shells. Our shoes, clothes and hands took on a brownish-yellow stain that lasted for weeks, and throughout the fall evenings were spent sitting in front of the fireplace cracking nuts. Until well after Christmas, the cakes and cookies that appeared every week on baking day were rich with nuts.

In my father's time, mast years were important. In those days the dominant forest tree was the American Chestnut, and each fall the whole family spent days in the woods collecting chestnuts for winter storage. Quantities of them were eaten… "roasted on an open fire" and otherwise… but the bulk of them were fed to pigs. In fact, many farmers simply turned their pigs loose in the woods for a month or so to fatten them on chestnuts. In mast years the pigs… and soon thereafter, the whole family… ate especially well. This practice ended in the late 1920's when the chestnut trees were all killed by blight, but 60 years later my father still wistfully recalled the taste of pork from pigs fattened on chestnuts.

Our forests have changed so much that it is hard to realize now how important the mast crop was. Before the end of the 19th Century, the most abundant bird in North America was the Passenger Pigeon; its numbers were estimated to be in the hundreds of millions. During migration season, flocks so dense that they blocked out the sun flew over for days. These enormous populations fueled their fall migrations by gorging on mast, particularly acorns and chestnuts. Incredibly, they were hunted to extinction… the last one died in the Cincinnati Zoo in 1916. Perhaps they were doomed anyway; whether they would have survived after the chestnut blight destroyed their main food source is an unanswerable question. Likewise, the primeval populations of deer, bear, ruffed grouse and wild turkeys that lived here in pre-colonial times were dependant on mast for their winter survival. All of these nearly became extinct in the mid-20th Century because of hunting and habitat destruction. They have made comebacks in recent years, but their future is by no means certain; gypsy moths now threaten the oak trees, and the entire forest ecosystem is under attack by the twin scourges of air pollution and development.

2003 is a mast year. After a series of dry years, we had an unusually wet summer with relatively moderate temperatures. The result has been a bumper crop of acorns, hickory nuts, beechnuts and walnuts. For the squirrels in my yard, this fall was a time to play; it didn't take long to store all the nuts they can possibly use, and next spring I expect to find oak and walnut seedlings popping up in my flower beds. Hunters tramping through the local woods will feel acorns under foot on every step, and the venison may taste a bit nuttier than usual. Perhaps Mel Torme's "Christmas Song" will have a little extra meaning this year.