Denver ? Instead of being told to stand back and observe, visitors to the latest exhibition at the Denver Art Museum are given magnifying glasses.

The best way to see a tiny drop of water among the leaves or other details in the 160 paintings of flowers in the Shirley Sherwood Collection is to be right on top of them.

“Many are so stunningly lifelike that one is drawn to look closely at them and marvel at the sheer skill of the painters,” says Brinsley Burbridge, until recently executive director of the Denver Botanical Gardens, and a longtime admirer of botanical art.

Visitors can see paintings of Amazon plants that are becoming extinct. The artists painted them to raise money in an effort to help preserve them.

“Some artists like the idea that they may be painting something for posterity,” said Sherwood, who began painting flowers at age 9.

Some show the several stages of the plant’s life, and take a year or more to paint. Unless an artist works from notes, he or she would need to wait for each cycle of life to tell the plant’s story.

The 160 paintings are from 465 paintings by 185 artists in Sherwood’s collection, the largest private collection in the world. The show will be followed by a smaller exhibition at the Smithsonian Institution March. The Denver exhibition ends Jan. 12.

Most of the paintings shown in Denver come from Great Britain, Sherwood’s and traditionally the center of botanical art. Works from artists in 25 other countries also are displayed. Most are done on vellum, using watercolors or gouache, a slightly more opaque watercolor.

Botanical painting had been considered a lost art, says botanist Burbridge, who recalls spending many hours 35 years ago studying flower paintings when he should have been studying the flowers themselves.

Although it began in 500 A.D., it reached its peak in 17th-century Holland. During “tulipmania,” everyone wanted to own one and they became so expensive it was cheaper to buy a painting.

Burbridge and other lovers of the art have worked to revive it and galleries have been set up showing what are sometimes called scientific illustrations or botanical illustrations. In 1995, the American Society of Botanical Artists was formed.

With the aid of a magnifying glass, a viewer takes a close-up look at the intricate detail of a 1978 botanical art painting entitled Sunflower by Australian artist Paul Smith, one of 160 pieces on display from the collection of Shirley Sherwood in the exhibit called Contemporary

Not all works in the Denver show simply focus on beauty. Mariko Imai’s “Insect Bitten Tree” is a study of what a parasite can do to a plant.

“Botanical illustration always had an assured future based on need: art in the service of science. Thanks to the Shirley Sherwood Collection it now has a future in the public eye,” said Burbridge.

Ever wonder what brussel sprouts look like before they are harvested? Ann Swan’s “Brussel Sprouts” makes the plant look positively elegant. A close look at Ludmyla Demonte’s “Passion Flower” reveals a hummingbird.

“I hope that people are amazed at what they see. I don’t think that you can take it all in at one time. We tried to make it accessible to people who are not experts so that you will at least know that you are in a room with tropical plants or Asian plants,” said Sherwood, who worked on the research team that developed the anti-heartburn medication Tagamet and has dedicated much of her life for the past decade to collecting the plants.

She has bought works from every continent except Antarctica; others she commissioned.

“I have been very fortunate to have met most of the artists,” she said.