If it were not for its color, the pistachio nut might have remained virtually unknown outside of its home grounds. It is agreeably flavored, sweet and midly exotic, suggesting a spice rather than a nut, but its taste is perhaps not sufficiently striking to have permitted it, over the years, to surmount the chief obstacle to its wide dissemination -- high cost. However, it possessed the asset of a color needed in cooking.

The appearance of food is important. It can please the palate without pleasing the eye, but if it pleases the eye it will please the palate even more. Taste is a mysterious phenomenon, to which psychological factors contribute greatly. One of those factors is color. It is probably most essential at the beginning of a meal and at its end -- color in hors d'oeuvres stimulates the appetite, color in desserts harmonizes with their gay, festive nature.

One color is lacking for desserts -- green. It is easy to find for other departments of the meal, but there are not many green foods consistent with the character of cakes, cookies, puddings, and the like. Angelica? Its range is limited. Fortunately, pistachio is there.

The pistachio nut itself is only a pale green, pleasing all the same when bits of it peep up at you shyly from the sausages and galantines in which it often is embedded. But its combination with the other ingredients of pastry and confectionery seems to confer heightened brilliance upon it. What other food tolerable in ice cream could give us the pronounced, though not overassertive, appetizing green it derives from pistachio?

The pistachio tree probably is a native of Persia and the territories contiguous to it. It still is grown today chiefly in this area, in a belt stretching from Afghanistan to the eastern end of the Mediterranean.

Only two species of its genus, pistacia, are cultivated to any extent elsewhere. One, the Chinese pistachio, pistacia chinensis, is grown almost entirely as an oranmental tree, because of its brilliant autumnal foliage. It bears nuts but I do not know if anyone eats them. It does play a minor role in the providing of food when it is used in California as rootstock on which to graft the plant which does give us the nuts of commerce, pistacia vera -- the true pistachio, also called the green almond. The other out-of-place pistachio is the only member of the genus native to America, pistacia mexicana, which, it is hardly necessary to inform you, grows in Mexico. It bears edible nuts.

Pistachio was eaten so long ago that its nuts have been found at the archeological site of Jarmo, dated at 6750 B.C., in what is now northeastern Iraq. However, the modest, retiring nature of the pistachio seems to have caused it be more or less neglected until about 2000 B.C., when, according to Reay Tannahill's "Food in History," an increase in population was probably what obliged the people of the Near East to exploit marginal foods which until then had been drawn upon usually only in times of shortage, among them was the pistachio.

From that time forward, the nut never was neglected in its native region. It was grown in the hanging gardens of babylon at the time of King Merodach-Baladan, about 700 B.C. It is one of the only two nuts mentioned in the Old Testament (the other is the almond).

Tradition says that the pistachio was brought to ancient Rome by the Emperor Vitellius, circa A.D. 50. One historian adds, "its price was exorbitant and even Apicius makes no mention of it." Judging from what else he used, Apicius would have been attracted rather than discouraged by extravagance. He delighted in calling for rare and costly ingredients (his chapter on poultry begins with ostrich.)

The fact that De Re Coqinari is silent about pistachio might induce suspicion on one or the other two points, if not both. The first: Is the traditional date ascribed to the appearances of pistachio in Rome not too early? The second: Is the Apicius cookbook an authentic ancient Roman work? Some experts doubt it.

In the other direction, the pistachio seems to have entered China not too long a time after the 6th centry A.D. when China began to develop contacts with the Near East.

The Persians used large quantities of ground almonds and pistachios to give body to desserts and sauces; the Arabs apparently learned this art from them, and medieval Europe perhaps from the Arabs, who exercised a considerable influence over European cooking during the centuries when they ruled in Spain and Sicily.

The Middle Ages went in heavily for sauces based on almonds, but they were more sparing of pistachios because of their cost, although medieval merchants in France were prepared to supply them to anyone who could afford it. The pistachio seems to have been first imported into England in the 16th century and had perhaps become generally accessible by the 18th century, when Mrs. Raffald's "The Experienced English Housekeeper," published in 1769, described the art of setting a table for after-dinner snacks and convivialty, including pistachios among the tidbits which should be offered.

They probably were intended to accompany the heavy drinking of those times, a function which they have not abandoned: Joan M. Jungleisch, in "For Innocents Abroad," proposes salted pistachios and roasted almonds as an ideal combination to accompany a social glass. Possibly this link between pistachio and alcohol lies behind the French expression prendre une pistache ("take -- or take on -- a pistachio nut"), which means to have a load on.

The anacardiaceae or cashew family, to which the pistachio belongs, is composed largely of tropical plants. The pistachio, however, is a plant of the temperate zone, though only the warmer parts. The only place where it can be grown successfully in the continental United States is California. Florida is warm enough, but too damp. The pistachio likes arid countries. California does indeed grow a limited number of pistachios, but most of the nuts consumed in the United States are imported, notably from Turkey.

Pistachios still are more expensive than most other common nuts, a circumstance which encourages adulteration or substitution, of which Alexandre Dumas already was complaining in his time. This is not easy, for pistachio possesses a flavor which is almost unique. The closest approach to it is not, as you expect, in its own genus, but in a different one. It is what the French call the falsh pistachio (and also, I don't know why, the nez-coupe, or cut nose), the European bladder nut, staphylea pinnata.

In Europe, the bladder nut seems to be eaten almost exclusively by German children, but the American bladder nut, staphylea trifolia, distinguished by the sweetness of its oil, is consumed by persons of all ages, probably in the belief that it is a pistachio.

In French, pistache de terre (earth pistachio) means the peanut, which, says the "Dictionnaire de l'Academie des Gastronomes," "is a real insult to the pistachio."