THERE'S AN INFALLIBLE LOGIC IN THE TECHNIQUE: To record the transitory characteristics of a plant or fish recently plucked from its environment, simply coat the specimen with ink, gently and carefully press a piece of paper over it, and voila! there before you is a tidy image, not lifelike, perhaps, but undeniably realistic. The scales of a fish, the veins in a leaf, the coarse ridges in a shark's fins are all represented clearly and accurately. But as this basic technique has developed over the years over centuries, really its practitioners have become concerned not only with accurate representation but with form and design. The resultant images are refined and delicate works of art, worthy of display. More than seventy such fish and plant prints will appear this summer at the California Academy of Sciences in a traveling exhibit entitled "Pressed on Paper: Fish Rubbings and Nature Prints."

Organized by the Santa Barbara Museum of Natural History and the Nature Printing Society, the exhibit has been touring the country's major museums for two and a half years, under the aegis of the Smithsonian Institution Traveling Exhibition Service. The exhibit opens at the Academy on 2 July and closes 18 September 1983.

The images are diverse, reflecting the varied history of the fish- and plant- printing methods. Plant printing in our cultural heritage appears to have developed in Europe in the 1400s. Leonardo da Vinci, for example, experimented with the technique. Later, in the 1600s and 1700s, plant prints were used as a precise means of illustrating herbals and botanical handbooks. The method survived into the 1900s, when the new science of photography pushed it into the background.

Fish printing comes from more recent Japanese traditions. There, the process is called gyotaku (gyo-fish, taku-rubbing) and was first practiced in the early 1800s by sport fishermen seeking a believable means of documenting the species and size of their catches. Gyotaku then developed into a popular art form.

Today, both fish printing and plant printing have many avid practitioners in the United States and abroad. The exhibit "Pressed on Paper" provides a comprehensive view of the best modern work.