Morton Arboretum celebrates Charles Darwin

When I think of evolutionist Charles Darwin and his 1859 "Origin of Species," I envision predator and prey, lions and gazelles, kings of the forest. I think of fauna, typically, not so much flora.

But when "survival of the fittest" is mentioned, I give you my backyard as Exhibit A. Creeping Charlie strangles the lawn that invades the coneflower beds which reseed themselves into perpetuity. It is most definitely a jungle out there.

The current exhibit at the Morton Arboretum's Sterling Morton Library, "Darwin's Flowers: Unlocking Natural Selection," shows how Darwin studied plants to help validate his theories of evolution. With colorful drawings, rare books and period artifacts, the exhibit illuminates Darwin's substantive forays into the vegetable kingdom.

Lectures at the library will augment the exhibit and honor the 200th anniversary of Darwin's birth and 150th year since "Origin of Species" was published.

"Darwin looked at plants in an ecological way, not old-fashioned taxonomy," says Michael Stieber, the arboretum's library administrator and reference librarian. Darwin's Victorian world included a popular fascination with botany and plant exploration, but much of the prevailing literature focused on plant structures and classification.

Darwin, who wrote six books on plants and pollinators between 1862 and 1880, aimed to demonstrate the principles of descent and modification by natural selection through plants. His famous transcontinental voyage on the HMS Beagle ignited his ideas of evolution, but also curtailed his future travels through an acquired illness.

"His debilitating health required him to work in greenhouses and (the) laboratory rather than taking extensive field trips," Stieber says.

Darwin's first plant-focused book, "Fertilization of Orchids," described how orchid structures were adapted to encourage pollination and perpetuation of the species. A craze for orchids had developed among Victorians, and Darwin's tropical travels offered hands-on knowledge of many species.

He demonstrated how the bee orchid's flower shape and scents mimic that of a female bee to lure a mate. Perhaps even bolder, he predicted the existence of an unknown creature with an unusually long proboscis that could be the only pollinator of the Christmas orchid, Angraecum sesquipedale.

The Christmas orchid's deep-set nectar spur defied other known methods of pollination. Yet a creature would need a proboscis of about 12 inches to partake of the nectar. The popular press and many early scientists mocked Darwin's imaginary winged pollinator. It wasn't until 1903 that the night-hawk moth with, as Darwin foretold, an extremely long proboscis was discovered in Madagascar, the native land of the Christmas orchid.

And it wasn't until this millennium that a photographer, with infrared equipment, captured the elusive nocturnal moth feeding on the orchid.

Darwin also wrote about plants' locomotive ability; the ability of twining plants, for example to bend and grow toward favorable conditions.

"Hold a tropical nasturtium petiole near a twig," Darwin wrote. "You'll see after about six minutes it will start to twine towards the twig."

We know now that plants are not sticks in the mud - phototropism, or movement to light, explains how plants can bend toward better light. It wasn't until 1928 that auxin, a plant hormone, was identified as the catalyst for phototropism. But through his observations and 1880 book, "The Power of Movement in Plants," Darwin explained the fundamental principles.

You could visit plant evolution gone amok in Exhibit A, my backyard. But you'd be much better informed and entertained by visiting the Darwin exhibit at the arboretum - it's the natural selection.

• Cathy Jean Maloney writes about nature and the Morton Arboretum in Lisle each month in Neighbor.

<p class="factboxtest12col"><b>If you go</b></p> <p class="factboxtest12col">What: "Darwin's Flowers: Unlocking Natural Selection"</p> <p class="factboxtest12col">When: Runs through Jan. 10</p> <p class="factboxtest12col">Where: The Morton Arboretum, 4100 Route 53, Lisle </p> <p class="factboxtest12col">Classes: </p> <p class="factboxtest12col">• "Trees of Life: On the Origins of Bird Species" at 7 p.m. Sept. 24. Trevor Price, professor in evolutionary biology program of the University of Chicago, discusses Darwin's theories in relation to bird species.</p> <p class="factboxtest12col">• "Charles Darwin, Botanist" at 7 p.m. Nov. 11 and 18. Michael Stieber, the arboretum's library administrator, explores Darwin's life, his trip around the world, and his pioneering studies of flowering plants.</p> <p class="factboxtest12col">Register: (630) 719-2468 </p> <p class="factboxtest12col">Info: mortonarb.org </p>