It's an ugly brown lump, homely as a potato, and a fast assumption would be that it's a starchy staple. It's the ji'cama, pronounced hee-cah-mah with the accent on the first syllable, and it's been showing up with increasing frequency at area supermarkets for several years.

You look at this vegetable and think a potato, albeit a large potato. You taste it and get a flavor and texture that is a cross between an apple and a water chestnut. Yes, it is a tuber, but it is a crispy, bright-tasting, new addition to salads and raw vegetable platters, and it is a new, low-calorie refreshing snack for the diet-conscious.

The ji'cama is a common snack food to Mexicans, who serve it in raw slices with a squeeze of lime and sometimes a quick dip into chile powder or salt. When sliced, it has a glassy wetness that is colorless, but its cool juiciness makes it very appealing in summer salads when combined with colorful vegetables.

The ji'cama (pachyrrhizus erosus) plant's legume is also edible and is known as the yam bean, but it is the round brown tuber that is showing up in markets here.

"We've carried it for several years, and there is no doubt it is growing in popularity," said Ernest Moore, spokesman for Safeway. It is available all year, but sometimes is in short supply in late summer, according to Moore. He said it is most popular with the Spanish community but feels a broader appeal is on the way.

Indigenous to South America and parts of Africa and Asia, the ji'cama was introduced by the Spanish into Mexico and Central America, where it is the basis of the classic Mexican salad -- Pico de Gallo, meaning "Beak of the Rooster." More on that later.

Since it is one of the exotics, what may look like an overgrown potato costs about a dollar a pound. The ji'cama comes in several sizes -- grapefruit to small pumpkin sizes -- but the smaller ones have a better texture. Look for unblemished firm tubers, those weighing under a pound. Besides the papery, thin brown skin, there is a fibrous layer beneath the skin. Both need to be peeled away before use.

While the vegetable can be cooked, its virtue is its simplicity as a raw snack and salad vegetable. Although it has a water content of nearly 87 percent (compared to an Irish potato's 75 to 80 percent water), it does have 1.6 grams of protein, 10 grams carbohydrates, about 15 to 18 milligrams each of calcium, phosphorus and ascorbic acid. It has only 46 calories per 100 grams. It's that shot of protein and ascorbic acid that make it a respectable food, said Raymond Webb of the Department of Agriculture Research Center in Beltsville. JI'CAMA AND ORANGE PICO DE GALLOS (6 servings)

The name Pico de Gallo refers to several Mexican salads with chopped ingredients and, according to legend, is named for the rooster that chops its food with its beak before eating. The ji'cama and orange version is a Mexican classic.

4 seedless oranges, peeled and sectioned

2 sweet red peppers, cut into thin strips

1 small ji'cama, about 3/4 pound, peeled, cut into matchstick julienne

Lettuce leaves for serving

Lime wedges for serving

FOR THE DRESSING:

1/4 cup white vinegar

1/2 cup safflower oil

1 teaspoon salt

1/4 teaspoon white pepper

1/4 teaspoon chili powder or paprika

1 clove garlic, peeled and crushed

1/8 teaspoon sugar

Salad ingredients may be prepared in advance and kept separate until ready to serve.

Combine dressing ingredients in a screw-top jar. Shake and set aside for several hours.

When ready to serve, toss together orange sections, red pepper and ji'cama strips with just enough dressing to give it all a light shine. Arrange lettuce leaves on a platter. Mound vegetables and garnish with lime wedges. Adapted from "Cuisines of the American Southwest" by Anne Lindsay Greer (Harper and Row, $22.50, 1983) JI'CAMA/HAM/CUCUMBER SALAD (6 servings)

1/4 cup coriander leaves, minced, divided

1 bunch escarole or bibb lettuce, washed, drained and patted dry

1 small ji'cama, about 3/4 pounds, peeled, cut into matchstick julienne

1/3 pound ham, thinly sliced, cut into strips

1 large cucumber, thinly sliced

FOR THE DRESSING:

3 tablespoons lemon or lime juice

1/2 cup light olive oil

Salt and white pepper to taste

Combine dressing ingredients with half the coriander. Shake, set aside.

Line a serving platter with lettuce leaves. Toss together ji'cama, ham and cucumber with a light drizzle of dressing. Serve on lettuce and sprinkle with remaining chopped coriander. DIANA KENNEDY'S ENSALADA DE JI'CAMA (6 servings)

2 small ji'camas (about 3/4 pounds each), peeled, cut into 1/4-inch cubes

1 heaping tablespoon fresh coriander, finely chopped

1 teaspoon salt

3/4 cup orange juice

1 teaspoon lemon juice

1 large naval orange, peeled and sliced

Lettuce leaves for serving

In a bowl, toss together ji'cama cubes, coriander, salt and orange and lemon juice and set aside to season for at least an hour. Serve on lettuce leaves garnished with orange slices. Adapted from "The Cuisines of Mexico" by Diana Kennedy (Harper and Row, 1972, $18.65). JI'CAMA/ORANGE/RED ONION SALAD (12 servings)

2 small ji'camas (about 3/4 pounds each), peeled and sliced paper thin with food processor or by hand

6 naval oranges, peeled and thinly sliced

2 medium red onions, thinly sliced

Lettuce leaves for serving

FOR THE DRESSING:

1/4 cup safflower oil

1/4 cup olive oil

1/3 cup fresh lime juice

3 tablespoons balsamic vinegar (or red wine vinegar)

1 teaspoon grated orange peel

Salt and freshly ground pepper to taste

Combine dressing ingredients in a screw-top jar. Shake and set aside.

Combine salad ingredients in bowl and toss with dressing, just enough to give a light shine to ingredients. Line serving bowl with lettuce leaves and fill with tossed salad.