A good melon ranks among late summer's most luxurious treats — melting yet still slightly crisp in texture, sweetly redolent of flowers or musk or honey, or all of them combined, depending on the variety. Can there be anything sweeter on a hot day than feasting on cool wedges of melon, draped with silken sheets of prosciutto?

But a bad one tastes like an undistinguished cucumber.

Telling the difference between the two is the key. And how you do that depends on a number of factors, depending on what kind of melon you're talking about (and, come to think about it, just exactly what it is you mean by "melon").

The good news is that once you've got a great melon, you're 90 percent of the way to a great dish.

When Alain Giraud was cooking at Bastide, a restaurant in Los Angeles, one of his signature appetizers was an almost paper-thin sheet of spiced cantaloupe wrapped around a crab salad. It was magnificent.

But even if you're not a star chef who can execute something so technically demanding, you can make great melon dishes. Some of the best are simple almost to the point of seeming Zen. Try serving a slice of melon with nothing more than a simple grinding of black pepper. The sharp, floral elements of the pepper are a perfect contrast to the lusciousness of the fruit.

For the same reason, greens including arugula, basil and mint seem to be natural accompaniments as well. You might never have thought of using such a sweet fruit in a savory salad, but given a restrained hand and the right mix of ingredients, it can be exactly right for a summer supper.

Really salty ingredients also are perfect foils for melon's sweetness. Cut a melon in chunks and drape it with prosciutto. Or spear a piece of melon on a toothpick along with a bite of salty dried sausage.

For dessert, lightly sauce sliced melon with a simple syrup flavored with mint and lime zest, or maybe slivered fresh ginger. Or cut a melon in half and fill it with either a muscat-based wine or port. White port is even better.

Some people purée melon and serve it as a cool, sweet summer soup for a first course. Personally, I'd rather have it as a dessert, maybe garnished with a little sweetened yogurt and some berries. It's but a short step from dessert soup to sorbet.

But before you get creative, you must have a good melon. And that's where things get complicated.

While once our choice of melons was limited, today you can find a wider assortment.

The other day, I came home with an orange-fleshed honeydew and a green-fleshed cantaloupe. I was just choosing the melons that seemed best. I wasn't wrong. The honeydew seemed to have all of that variety's floweriness, but with a more luscious texture. The cantaloupe seemed even sweeter than normal, with its musk lightened by a little honey.

Because family matters so much with melons, choosing the right one must begin with a little lesson in botany. Melons are members of the gourd clan, along with squashes. Collectively, these are known as cucurbits. The specific family that includes most melons is Cucumis, which also includes cucumbers.

Within the Cucumis family, melons are divided into several groups. The first group is called inodorous. They are smooth-skinned melons such as casaba and honeydew. They usually have green flesh, but not always. Inodorous melons tend to be very sweet, have a fairly crisp, slightly grainy flesh and a honeyed quality to the flavor.

The second group is cantalupensi — melons with rough skins and usually with orange flesh. These include cantaloupes. But wait. What you probably think of as a cantaloupe isn't a cantaloupe at all. It's a muskmelon. Some botanists recognize a third class of melons, which have netted skins. They call these reticulatus, and the melon we call a cantaloupe is one of them.

Fortunately for cooks, other than the texture of the skin, cantalupensis and reticulatus melons are pretty much the same: Their texture is smoother than inodorous melons; they might be slightly less sweet, but their flavor and aroma are more powerfully floral, almost musky.

Attempting to memorize the ins and outs of the various melon families would be a Sisyphean task. Instead, just keep in mind the difference between the smooth-skinned and rough-skinned melons, because each of these families reveals its quality in different ways.

Rough-skinned melons are the easiest to choose, because they give you so many clues. The first thing to check is the netting or scaling. In a mature melon, this will be tan or golden in color and definitely raised above the background skin, which should be golden in color, not green. Some rough-skinned melons are also ribbed. In a mature melon, those ribs will be pronounced.

Inspect the skin also for the pale, smooth spot the French call the "couche," which is the place where the melon rests on the ground. It should be creamy or golden. It, too, should be pronounced, but ideally not too much so. If there is no couche, it probably means the melon was picked too early. If the couche is too big, it's a sign that the melon rested in one place for too long.

A clean bellybutton is important, but you knew that, right? All rough-skinned melons are harvested at what farmers call "full slip," which means the fruit pulls cleanly away from the vine, leaving no trace of a stem in the bellybutton.

One of the best ways to choose a rough-skinned melon is also the most obvious: Give it a whiff. When fully ripe, these melons develop a heavenly musky floral perfume that you can smell at the other end of the produce section. Remember, though, that it is but one step from fully ripe to overripe. Melons can be too soft and too fragrant.

The only one of these clues that works for smooth-skinned melons is the couche. There's no way around it: These fruits are devilishly hard to choose. The first thing to look for is color. This is extremely subtle, the difference between a "hard" green or white and a "creamy" color. But if you look at several, you'll see the distinction. Although the skins of these melons are smooth, when they are fully mature they will develop a slightly waxy texture.

The best indicator of quality I've found in smooth-skinned melons is what growers call "sugar spots" — brown flecks on the surface. Unfortunately, you'll see them only at farmers markets; supermarket produce managers tend to regard them as imperfections and wash them off.

Remember that there is a difference between ripeness and maturity. Melons will continue to ripen after picking — the flesh will soften and the aromas and flavors will become more intense — but they won't get any sweeter. This softening is usually most evident at the blossom end of the fruit. Press gently; if there is a little give, the melon is ripe.