Browse through the seed catalogue of Virginia's Southern Exposure, but don't expect the usual Better Boys and Beefsteaks. You will find the Brimmer, the Virginia tomato that won the grand prize at the Jamestown Exposition sometime around 1910.

In the catalogue for the 206-year-old Landreth's Seeds Co. of Baltimore, there are 63 plant varieties "sold in the years of the 1800s" by a company that counted George Washington and Thomas Jefferson among its customers and still supplies seed to Jefferson's Monticello.

Harrisonburg, Va.'s Wetsel Seeds, a relative sprout at 73, began in the back of the wagon from which Bob Wetsel's grandfather sold seeds on court days in Shenandoah and Rockingham counties. More recently, it's been acquired by Southern States Cooperative Inc., but its catalogue still contains the garden calendar for eastern Virginia and North Carolina.

They aren't titans in the $4 billion-a-year industry better known for its bigger players, such as garden seed suppliers Northrup King and W. Atlee Burpee Co. and farm supplier Pioneer Hi-Bred, but these smaller seed companies still are a major part of the business.

Playing an important part in preserving the nation's agricultural heritage and diversity, they are garden-variety companies in a very different sense, according to environmentalists and agricultural researchers.

Some are old, family-run businesses, such as Landreth's, the nation's oldest seed company. Others, such as Southern Exposure, based in North Garden, Va., 15 miles south of Charlottesville, are niche marketers that cultivate and sell older "heirloom" varieties of fruits, flowers and vegetables with the stated goal of preserving plant varieties that might otherwise be lost.

In recent years some botanists and environmentalists have warned that consolidation in the seed industry, and market pressures that favor seeds that can be widely grown over those developed to work in a particular region, may threaten agricultural genetic diversity -- and, in turn, the vitality of farm crops.

"To breed for a particular valley's problems is not something a university gets particular tenure points for," said Gary Paul Nabhan, president of Native Seeds/SEARCH, a nonprofit seed conservation organization. "There's really been a profound drop in this type of activity that aids small farmers and regionally adapted agriculture," he said.

The concerns about genetic diversity generally focus on the staples of agriculture, such as corn, wheat, cotton and soybeans, rather than garden vegetables or flowers. The issue first arose in the 1970s when blight wiped out approximately 15 percent of the U.S. corn crop, which was vulnerable because most of the varieties being grown shared a common genetic background. U.S. Department of Agriculture researchers say that a disaster like the corn blight is less likely now because farmers are more alert to the possibility.

"We see absolutely no loss of product," said David Lambert, acting executive vice president of the American Seed Trade Association. "As a matter of fact, product proliferates over what it used to be. Farmers and home gardeners have far more choice than they used to."

At the same time, however, some older varieties of fruits, flowers and vegetables have become harder to find as they are replaced with varieties that breeders and seed sellers felt had more to offer. While their disappearance may not threaten agriculture, there appears to be an increasing interest in preserving or reviving some of the older varieties.

Some companies, including Southern States, founded as a seed supply cooperative in 1923, still offer old varieties. "We keep stocks of older varieties like White Half Runner bush beans, and there are many other vegetable varieties of the older kind that we grow, but some of these older ones are passing from the scene," said Gil Barber, manager of seed procurement and the seed laboratory for Southern States.

Still other firms seek out varieties that may have been handed down from generation to generation within a family, keeping them alive long after they fade from the commercial scene.

"In general there have been two simultaneous trends that don't necessarily balance each other out," said Nabhan. "More than 100 regional and national companies have been bought out. At the same time, we've seen a proliferation of small family- or cooperative-owned companies that specialize in regionally adapted heirloom seeds. These have developed a new market that, in some ways, provides a new source of regionally adapted seed to replace ... the older companies."

Southern Exposure is part of that wave, offering Mortgage Lifter tomatoes, Ruth Bible beans, Deer Tongue lettuce and other varieties not found in most seed catalogues. The company started eight years ago as a small family owned business, said Jeff McCormick, who owns the company with his wife, Patty Wallens.

"Our focus has been on trying to identify and maintain regionally adapted varieties," McCormick said. "We're always looking for varieties that have interest. It doesn't have to be commercial interest -- just any variety that has any particular characteristic that is worthwhile or is not in general circulation."

The first Southern Exposure catalogue, published in 1983, offered 65 varieties, and the company had 197 customers. Since then the mailing list has grown to a figure that McCormick says is in "the five digit range," and the company now offers more than 500 varieties, he said, shipping nationwide. McCormick declined to be more specific about either the size of the list or his earnings from the seed business, which he described as intensely competitive. He said he gets about a 33 percent return rate from his mailing list, however, and that the company has been profitable since 1986. The catalogue costs $3. McCormick said Southern Exposure's gross sales have risen each year -- doubling, on average.

Although McCormick and Wallens grow some of their own seed, most of it comes from growers with whom they contract. "A lot of the seed that comes in from growers, we have to do further processing of. We do further cleaning and germination-test it." The seed is also packed and stored at North Garden. Much of the seed arrives around December; the orders come in from January through May.

Catalogue entries describe the history and qualities of the varieties offered. Mortgage Lifter tomatoes, for instance, were developed in the 1930s by a West Virginia radiator repairman who crossbred four of the largest-fruited varieties he could find. His creation, which the catalogue says can produce fruit weighing four pounds apiece, got its name by being so popular that it enabled the mechanic to pay off his mortgage in six years.

Southern Exposure also offers Stringless Red Valentine bush beans "introduced by Landreth's in 1832 and improved as a stringless variety by Landreth's in 1930."

Landreth's, located on West Ostend Street in Baltimore and in business since David Landreth founded it in 1784, is one of just a few survivors of what was once a more active seed industry in the city, according to Vincent S. Goldberg, president of the company. Goldberg, who founded and owned another seed company, acquired the business from the Landreth family 22 years ago. "At present we're selling seeds coast to coast," said Goldberg. "We're not the biggest seed dealer like we used to be, but we sell coast to coast to gardeners and to dealers, seed companies, feed companies and hardware stores."

The catalogue is published about every five years and updated annually with a price list. Landreth buys its seed from growers, most of them on the West Coast, where most seed companies now get their product.

"We have a list which we contract to have grown for us," said Goldberg. "As a rule, some {seed varieties} are very hard to find altogether because they are not as popular anymore, although some varieties, some old varieties, I personally like better than the new varieties."

Western growers also are a source for Wetsel Seeds, thanks to Northern Virginia's growth. "We used to do a lot of processing of seeds that were grown reasonably locally," said Bob Wetsel. More recently, though, growing has "been concentrated into parts of the country where the land isn't as valuable as ours. A lot of seed that we used to grow and ship out was grown out near what is now Dulles."

Southern States Cooperative acquired Wetsel in December, but the family will continue to run it as a subsidiary, said Wetsel. The company has a retail outlet, its main office and a distribution center in Harrisonburg, and two sales offices and warehouses in Virginia Beach and Kittanning, Pa., near Pittsburgh.

Although Wetsel also has a catalogue sales operation, most of its business is selling to retailers -- nursery operators, lawn and garden centers and hardware stores. Over the years it has diversified into "allied products" such as fertilizers, tools and bird feeders. "It's not quite as seasonal, and it gives you a better base," said Wetsel, whose brother, two sons and a nephew also help run the business.

The company anticipates virtually no change in its business under its new owner, a farmer cooperative based in Richmond. Southern States also began as a seed company, although it, too, has expanded into other product lines. In its most recent fiscal year, ended June 30, 1989, it sold $38.5 million worth of seeds -- a lot of seeds but only a small part of its revenue, which is expected to be about $900 million this year.

Southern States gets most of its seed from western growers, but the cooperative tests varieties for local use at its research farm east of Richmond and sells several exclusive brands of garden seeds, said Don Tindall, assistant director of corporate communications. They include the Statesman tomato and Cotton Candy corn.

Southern States also owns, along with other cooperatives, a research farm near Purdue University in Indiana where research is done on crops such as corn, soybeans, alfalfa and clover.

"Every company is not selling the same thing," said Barber, who is also chairman of the research facility. "A lot of seed companies are doing more research than they ever have. And the biotechnology companies are on the scene. There's a lot of money being spent. We're doing some of both: We're preserving some of the old and are introducing new varieties... ."

Getting Down to Grass Roots

Strick Newsome is a specialist in lawn order. He and his wife, Betty, own Newsome Seeds in Rockville, a company that distributes grass seed to professional landscapers in Maryland and Northern Virginia.

The company also sells grass seed for erosion control and to golf courses and sod farmers. Unlike some of his competitors, Newsome has so far declined to branch out into other products.

Newsome buys much of his seed from growers in the Willamette Valley of Oregon, where "the farmers get very good yield and can grow it cheaper," he said.

He also gets seed from an area around Missouri and an area near Spokane, Wash.

What's Washington, D.C.'s favorite grass? Tall fescue, perennial rye, annual rye, Kentucky bluegrass and fine fescue are the primary varieties grown in this area, he said.

"All the northern, cool-season grasses grow from here north. Zoysia and Bermuda grass grow from here south. This area is in a transition area," which is good for his business, he said.

"You can grow either northern cool or southern warm. Both grow, but neither do very well."

Newsome's wholesale operations are busiest in spring and fall. The company is profitable, he said.