IN MEDIEVAL Japan, there grew up a tradition of farmers/potters, who made great urns or storage jars to keep their grain and pay their tribute to the local warlord. They potted during the dark winter months, using their kiln firings to help keep warm, and farmed during the good weather.

No other type of ceramic has the strength, and perhaps the arrogance, of these strong works. They are unglazed, colored only by the fire and the occasional deposit of ash. Yet every centimeter is a different color from the next. The textures are as unexpected as the colors, rough and varied as the earth itself.

Two of these extraordinary works are now on view at the Freer Gallery of Art as part of a small but scholarly exhibit of 50 pieces of Japanese ceramics. Louise Cort, who wrote the informative monograph that accompanies it, selected the show to point out the origins of the Japanese ceramic tradition continued in a larger exhibit, "Japanese Ceramics Today: Masterworks From the Kikuchi Collection," across the Mall at the Museum of Natural History. This show continues through April 3.

The Japanese have spent 12,000 years perfecting their techniques to produce the ultimate in shape, texture and color. Fortunately, each new technology has added to the old knowledge, not supplanted it. Many of today's potters are using techniques directly derived from neolithic to medieval potters.

The early 16th-century (Muromachi) jar from the Echizen kiln, a new acquisition for the Freer, is a prime example of these early masterpieces. The jar was made of unprocessed local clay (as was all the stoneware of this period), producing the distinctive colors.

On the Echizen pot, you can see the incised signature of the potter, placed there to differentiate his work from its kiln mates. In those days, the entire village would build the kiln and share its use. It would take perhaps six weeks to bake a lot, with all the villagers taking turns feeding the kiln.

Scholars had thought there were only six such major kilns. But recent excavations show more than 30, according to Cort, who studied in Japan many years to write "Shigaraki, Potters' Valley." Some of the kilns are still producing wares.

(Currently there is a movement among American potters to try out these early techniques. So far eight wood-fired kilns of the archaic tunnel anagama type have been built in the United States, one near Charlottesville.)

A Jo-mon earthenware storage jar, circa 3000-2500 B.C., also is on display. Its curlicue decoration on the rim, and the designs both incised and in relief on the body of the jar, are remarkably sophisticated. And a smoke-blackened bowl on a pedestal foot, similar to Korean vessels, is Sue ware from the sixth century Tumulus period. Although it looks like a goblet, it was used for the ceremonial presentation of solid food.

Other important pieces include an Oribe (named after a tea master) fish dish, early 17th century, with a bamboo-shaped handle and a base shaped like a fan (an open fan signifies luck opening up); a Yayoi (first century A.D.) ceremonial jar with red iron oxide coating, found in a burial site under the modern city of Fukuoka; an underglaze copper-red Shigaraki stoneware water jar for hand washing, circa 1865, made by Okuda Shinsai, who was as famous a sumo wrestler as he was a potter; and a small sake bottle, a Tamba ware, from the 1830s, made by Naosaku, said to float in hot water when filled with sake.

The Freer exhibit continues through Aug. 31.