“The Hengduans were a safe haven for plants in the ice age,” says Yin, while passing through an alpine meadow. “And there is a great range in the altitude, so there are many small climate zones. That’s why we have so many species of plants and so many that can be adapted to Western gardens.”

Wiry and fit, Yin wears his 63 years lightly and is readily amused. He erupts with a hearty laugh when I ask him how many times he has hunted for plants in this meadow. “Many times. Many, many times. Wilson too. He came here looking for seeds of the yellow poppy, Meconopsis integrifolia.”

From the Min River valley, we traveled up and down various parts of the Hengduans, sometimes following the exact path where Wilson had trod, other times veering away to see what Yin described as“something special”: the original wild crab apple tree (Malus theifera), for instance, or a rambling yellow-blossomed clematis, still in bloom in the autumn. The mountains’ lower slopes were dense with oaks, maple and magnolia trees, wild lilacs and hydrangeas, and dozens of different rhododendrons—many of which Wilson collected and are now found in pure or hybridized varieties in Western gardens. Roses with spines the color of garnets twined their canes among trees, and in the shade, wild strawberries, butterfly bushes, and anemones bloomed. We passed wild plum and apple trees laden with fruit, then moved into a coniferous zone, where Yin started to carefully point out each kind—spruce, larch, silver fir, pine, cypress, identifying each by genus and species—Picea likiangensis, Abies squamata, Larix potaninii, Pinus densata—before laughing and saying: “Well, we have 50 conifer species. Too many!”

We stopped at a mountain pass some 14,000 feet high and close to the Tibetan border. Around us, snowcapped mountains marched shoulder to shoulder to the far horizon. In the States, of course, these elevated landscapes would be above the snow line, lacking vegetation. But here, plants can eke out a living at 17,500 feet. Between the mountain peaks, deep river valleys cut their way through the Hengduans, including four of Asia’s largest rivers—the Mekong, Yangtze, Irrawaddy, and Salween. From the valley bottoms to the snow line, the mountains include six different vegetation belts: a warm-temperate zone that stops at 2,000 feet and is home to palms, bamboos, pines, and cypress trees; a temperate zone from 2,000 to 5,000 feet of rain forest with oaks, hollies, and ferns; a cool-temperate zone from 5,000 to 10,000 feet of mixed deciduous trees, conifers, and rhododendrons; a subalpine zone from 10,000 to 11,500 feet of dense coniferous forests, larch and spruce trees, and more rhododendrons; an alpine zone from 11,500 to 16,000 feet with grasslands carpeted in herbs, primroses, poppies, gentians, and small-leaved rhododendrons; and an alpine desert from 16,000 to 17,500 feet of tiny-leaved herbs and cushion plants. Combine this with a monsoonal climate, and you get what Wilson called “a botanical paradise,” a region with “beyond question, the richest temperate flora in the world.”

Even on this high, chilly mountain pass, it took Yin only minutes to locate alpine species that Wilson and other European plant hunters had discovered. Their domesticated descendants grow happily in American and English gardens. Among the grasses, gentians turned their rich blue trumpets to the sun, while yellow, star-shaped sedums nodded in the breeze. Diminutive azaleas, bright with jewel-blue blossoms, blanketed a slope, and in a damp spot, Yin pointed out a tall primrose, Primula wilsonii, the first plant named for Wilson and one that he collected in 1900, on his first expedition.

“Professor Yin knows all the plants because he’s walked all over Sichuan, touching each kind,” says Chang. “He’s walked maybe 30,000 kilometers [18,000 miles], and he says he even crossed this pass twice on foot—and so did Wilson.”

“It was part of my job,” Yin says. “After high school, when I was 18, the government assigned me to the Chengdu Institute of Biology. They didn’t ask you what you wanted to be. They told you. But it was fine with me. I liked the idea of traveling and running around in the mountains.”

Yin had graduated in July 1960. One month later, he was camping in a forest and collecting plants with Liu Zhaoguang, a professor from the institute who became his mentor. “I was Professor Liu’s assistant, so I would collect the plants he or his colleagues told me to get and press them for herbarium specimens,” Yin says. “Then he taught me how to identify the plants, how to key out their classification. And that was how I found Wilson.”

In the Linnaean taxonomic system, the name of the person who discovers a new species may be added after the plant’s name. Sometimes, as in the case of P. wilsonii, a plant species may be named for the person who found it. Wilson’s name appeared many times in Yin’s plant identification book.

“Of course, many plants that Wilson and the other European botanists found were already known here in China,” Yin says. “We had 2,000 years of botanical study and knowledge, especially about medicinal plants. But the Western explorers brought the modern, scientific system—Linnaean taxonomy—to China. So I see them as the forefathers of modern Chinese botany.

“And look at how hard they had to work,” Yin says, making a sweeping motion with his arm at the surrounding rugged terrain. “There were no roads here then, no cars. They did all their work on foot and in a foreign land. No matter where they came from, we must respect them and their science and what they gave China and the world. They used our plants and their botany to build a bridge between East and West.”

That bridge collapsed in the late 1930s as political unrest swept through China. When the country emerged under the leadership of Mao Tse-tung in 1949, it no longer welcomed Western scientists. Until then, foreigners had done most of the geologic, zoological, and botanical studies in China. Mao decided to change this, and in 1960 launched broad natural history surveys across the country.

“Mao felt it was time for Chinese scientists to do this work,” says Yin. “We needed to survey our own biological resources and record the data in our language. And I was assigned to Professor Liu as his apprentice to help on the survey.”

Liu and his colleagues were charged with compiling a botanical survey of the entire Sichuan Province. They would collect the plants in every terrain: mountains, river valleys, alpine plateaus, and low-lying agricultural lands. To appreciate the size of the project, it’s worth noting that in a mere four days on a mountain near Chengdu, Wilson had collected 220 species of plants. And those were plants that struck his fancy and seemed worth bringing to the attention of the commercial nursery that employed him. Yet despite the scope of the provincewide survey, Yin says the botanists at the institute didn’t hesitate or complain. “It was our job, so we did it. But it took a very long time”—eighteen years, with a crew of eight men.

Over those years, Yin changed from a teenager who simply loved being in the fresh air to a serious scientist, a mapmaker who compiled the plant-distribution map of Sichuan, and an ardent conservationist. “It was easy to see that the forests were being destroyed, even while we were collecting the plants in them,” Yin says. The provincial and national governments had promoted the timber industry in Sichuan as a way of employing people. Lower-elevation forests were rapidly being converted to farmland. “We were losing species,” Yin says. “Actually, this was also happening in Wilson’s day; he also wrote about this destruction and how it was important to save some of the original forests. I agreed with Wilson.”

Today there are more than 40 parks in Sichuan—20 created at Yin’s instigation. Logging has been banned to prevent environmental degradation and flooding. “We’ve changed the focus to preservation and ecotourism,” Yin says. One of the province’s newest reserves, Yading National Park, opened three years ago. It lies along the Sichuan-Yunnan border, and two days of hard driving from the pass brought us to its mountain-hemmed valleys. Wilson never made it this far into Sichuan, although American botanist Joseph Rock did. Rock sampled plants here, but the real collecting was done in the 1970s by Yin and the institute’s survey team.

We were now exclusively in Yin territory, as we rode mules into Yading, following a wide trail beside a meandering, jade-colored river. Yin’s modesty held him back, but the park had been largely his doing. He loves Yading’s forested mountains and the Tibetan people who live here: “I told them they should never cut a single tree—that it was so beautiful, one day many tourists would come. And you see, that has happened.”

The forest here is dense with conifers and hardwoods and a thick understory of willows, shrubby barberries, daphne and cotoneaster bushes, bamboos, astilbes, honeysuckles, and ferns. The mix of vegetation is startling, and wherever we turn, I inevitably spot plants I recognize from gardens—yet they are very much at home in the wild.“It’s even more of a garden on the opposite side of the mountain,” Yin says. “There we would see palms and orchids together with the conifers. And there’s a big region there that is still unexplored. That’s my new dream: to explore it and find new plants. We got most of them on our big survey, but there are always more to be found.”

We stop to rest on boulders below a small Tibetan Buddhist monastery. From the valley floor, the mountains rise abruptly, their steep flanks rumpled and bristly with vegetation. Yin shakes his head. He remembers how he and the other team members climbed up and down these forested slopes.

“We climbed all these mountains,” he says. “We were following the international protocol for botanical surveys. And so we collected everything on a vertical track from this valley to the snow line. Then we would go to another site and do it again.” At each site, they marked off small plots and measured the amount of forest and shrub cover. Then team members counted the number of plants of each species in each plot. Yin would later transfer that data to his plant-distribution map. “Honestly, I have to say it was very boring work,” he says. “We did the same thing day after day, month after month, year after year. Unless you loved botany and science, you wouldn’t do it. But by then, I loved both.”

During his first year as an apprentice botanist, though, Yin had not felt such passion for the work. That came after what he calls his “big mistake.” The transformation happened in the summer of 1961, after one of Professor Liu’s colleagues sent him to collect plants from three wetlands sites south of Chengdu. At the time, people were starving throughout China because of Chairman Mao’s failed agricultural policies.

“Everyone was hungry,” Yin recalls. “There wasn’t enough food for anyone and certainly not for young traveling botanists. My biggest wish always was to have a full stomach. From morning to night, I was hungry, hungry, hungry. But so was everyone.”

He walked 30 miles to the first site, passing dead and dying people along the way. “I had never seen such a thing,” he says, shaking his head. When he reached the government lodging, where he was to be housed for a week, he discovered there was nothing to eat except one bowl of bamboo shoots and the leftover mash from making soy milk each day. The combination was so foul that he sometimes vomited or contracted debilitating diarrhea. His legs and belly began to swell from malnutrition.

“I found the first place the professor sent me to. There were many plants, and I grabbed a big armful. I divided them into three bags, and I thought to myself, ‘Okay, he wants three piles of plants. These will do.’ I didn’t go to the other two sites. I was too hungry, and I cheated.” When Yin returned to the institute, he presented the professor with the three bags of plants. The botanist looked at the samples, then turned to Yin and asked, “Did you really go to all three sites?”

Yin remembers how his face flushed hot and red because of  the professor’s question. “I still looked him in the eye and said yes. He knew that I was lying. He knew the plants, and he knew these were not the right ones. But he didn’t complain or criticize me. He didn’t say anything.”

That night Yin could barely sleep. “From this I learned the ethics of being a scientist and the importance of honesty in collecting,” he says. “I vowed I would never cheat again and that no matter how hungry I was, I would go as far as necessary to do my work correctly. But I have to thank that mistake. It’s because of my lie that I became successful. It made me a true man of science.”

Yin rises from his rock, and we walk up a steep trail into the forest. Climbing roses, yellow-leaved willows, white-flowered thalictrum, and primroses grow alongside the mountain path in profusion, while a mix of conifers tower overhead. Along the way, Yin keeps up a steady litany, reciting the names of the various plants we see. And then he suddenly stops. “He wants to say more about his mistake,” says Chang, turning to resume her interpretation. “He says, ‘A life is made from a series of accidents,’ ” she begins, then segues into pure translation. “I never thought about being a botanist. And I don’t think Wilson ever thought as a boy about collecting plants in China. But that is what we both did. And now the world has the benefit of all these plants.” Yin stops talking. He casts his eye up and down the forested slope in front of us. “It really is like a garden, isn’t it?” he asks. “It really is a Chinese garden wilderness.”