The strangler fig is even more sinister. Its seeds germinate in the branches of other trees and send out roots that slowly grow down toward the ground. Once the end touches the soil it takes root. The roots hanging down all around the support tree grow into saplings that will eventually strangle the host. I was awestruck when I saw the famed temple at Angkor Wat in Cambodia, utterly embraced by the gnarled roots of a giant and ancient strangler fig. Tree and building are now so entwined that each would collapse without the support of the other.
The so-called clonal trees have remarkable root systems that seem capable of growing over hundreds of thousands of years. The most famous of them—Pando, or the Trembling Giant—has a root system that spreads out beneath more than 100 acres in Utah and has been there, we are told, for 80,000 to one million years! The multiple stems of this colony (meaning the tree trunks) age and die but new ones keep coming up. It is the roots that are so ancient.
The variety of leaves seems almost infinite. They are typically green from the chlorophyll that captures sunlight, and many are large and flat so as to catch the maximum amount. Indeed, some tropical leaves are so huge that people use them for umbrellas—and they are very effective, as I discovered during an aboriginal ceremony in Taiwan, when we were caught in a tropical downpour.
Orangutans have also learned to use large leaves during heavy rain. My favorite story concerns an infant, who was rescued from a poacher and was being looked after in a sanctuary. During one rainstorm she was sitting under the shelter provided but, after staring out, rushed into the rain, picked a huge leaf, and ran back to hold it over herself as she sat in the dry shelter.
Some leaves are delicate, some are tough and armed with prickles, yet others are long and stiff like needles. The often-vicious spines of the cactus are actually modified leaves—in these plants it is the stems that capture the energy from the sun. I used to think that the brilliant red of the poinsettia and the varied colors of bougainvillea were flowers, but, of course, they are leaves adapted to attract pollinating insects to the very small, insignificant-looking flowers in the center.
And then there are the most extraordinary leaves of that bizarre plant Welwitschia mirabilis. Each plant has only two leaves. They look like quite ordinary, long-shaped leaves on young plants, but they continue to grow, those exact same two leaves, for as long as the plant lives. Which may be more than 1,000 years. The Welwitschia was first discovered in Africa’s Namib Desert by Dr. Friedrich Welwitsch in 1859 and it is said that he fell to his knees and stared and stared, in silence. He sent a specimen to Sir Joseph Hooker, at Kew botanical gardens in London—and Sir Joseph for several months became obsessed with it, devoting hours at a time to studying, writing about and lecturing about the botanical oddity. It is, indeed, one of the most amazing plants on Earth, a living fossil, a relict of the cone-bearing plants that dominated the world during the Jurassic period. Imagine—this gangly plant, which Charles Darwin called “the duckbill of the vegetable kingdom,” has survived as a species, unchanged, for 135 million to 205 million years. Originally, its habitat was lush, moist forest, yet it has now adapted to a very different environment—the harsh Namib of southern Africa.
If plants could be credited with reasoning powers, we would marvel at the imaginative ways they bribe or ensnare other creatures to carry out their wishes. And no more so than when we consider the strategies devised for the dispersal of their seeds. One such involves coating their seeds in delicious fruit and hoping that they will be carried in the bellies of animals to be deposited, in feces, at a suitable distance from the parent.
Darwin was fascinated by seed dispersal (well, of course—he was fascinated by everything) and he once recorded, in his diary, “Hurrah! A seed has just germinated after twenty one and a half hours in an owl’s stomach.” Indeed, some seeds will not germinate unless they have first passed through the stomach and gut of some animal, relying on the digestive juices to weaken their hard coating. The antelopes on the Serengeti plain perform this service for the acacia seeds.
In Gombe Stream National Park in western Tanzania, the chimpanzees, baboons and monkeys are marvelous dispersers of seeds. When I first began my study, the chimpanzees were often too far away for me to be sure what they were eating, so in addition to my hours of direct observation I would search for food remains—seeds, leaves, parts of insects or other animals—in their dung. Many field biologists around the world do the same.
Some seeds are covered in Velcrolike burs (Where do you think the idea of Velcro came from, anyway?) or armed with ferocious hooks so that a passing animal, willy-nilly, is drafted into servitude. Gombe is thick with seeds like this and I have spent hours plucking them from my hair and clothes. Sometimes my socks have been so snarled with barbs that by the time they are plucked out, the socks are all but useless. Some seeds are caught up in the mud that water birds carry from place to place on their feet and legs.