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Reading Darwin’s “The Various Contrivances by Which Orchids are Fertilised by Insects”

March 8, 2009
New York, N.Y.

I guess a lot of people will be reading books by Charles Darwin this year in celebration of the bicentennial. Although Darwin is best known for a couple books on evolution, he wrote more than 20 books during his lifetime, as can be discovered in the Wikipedia article List of Works by Charles Darwin. Many of Darwin's later books are on botanical subjects; he seemed particularly interested in plant fertilization, movement, and feeding habits.

Reading even the more obscure books by Darwin has never been easier: The Complete Works of Charles Darwin Online features side-by-side text and image views as well as PDFs. You might also try Google Book Search for original editions, and if you actually want to buy something, AbeBooks is a great source for used books. First editions of Darwin books are expensive, of course, but later editions and printings published by John Murray (Darwin's London publisher) or D. Appleton (his New York publisher) can be reasonable (i.e., in the mid two figures).

Darwin's first book after The Origin of Species (1859) was entitled On the Various Contrivances by which British and Foriegn Orchids are Fertilised by Insects, and on the Good Effects of Intercrossing (1862), a very focused book and (like all of Darwin's research) based on close personal observation and experimentation. The revised second edition published in 1877 had a somewhat shorter title, The Various Contrivances by Which Orchids are Fertilised by Insects, and added some new research from the intervening 15 years, including some gracious admittances by Darwin of previous errors. I read an 1885 printing of the second edition (in a facsimile edition from Elibron) and unless otherwise indicated, the page numbers I cite are from the second edition. The book is quite short (about 300 pages) and well worth the time.

Like most animals and plants, orchids achieve greatest generational health through cross-fertilization, and they have evolved to help ensure that cross-fertilization occurs. Insects (generally flies, moths, bees, and butterflies) are attracted to orchids in various way, including the promise of nectar. The insect generally lands on the labellum, which is modified petal found in the center of the orchid between the other two symmetrical petals. When the insect enters the flower and disturbs an inner part called the rostellum, it ruptures, causing part of it — a disk coated with a viscous fluid, attached by a caudicle to a pollinium, which is a collection of pollen grains — to stick to the insect. Sometimes this sticks to the insect's proboscis, or leg, or head, or even eye. When the insect leaves the flower, the caudicle bends somewhat as it dries so that by the time the insect visits another flower, the pollinia is aligned in the right way to dump pollen on the stigma, which fertilizes the plant.

There are many species of orchids, of course, and they are all built somewhat differently, and throughout The Various Contrivances..., Darwin describes the workings of many of these variations. This is a very personal book: Darwin describes to us the experiments he performed, and shares his struggles to understand particularly tricky configurations. Darwin mentions many of his correspondents and helpers around the world, as well as research in orchids performed by three of his sons: William (1839 – 1914), George (1845 – 1912), who later did important research on tides and tidal friction, and Francis (1848 – 1925), who later edited his father's autobiography and letters.

Despite the seemingly dry nature of the subject, the general tone of The Various Contrivances... is that of sheer joy. As Darwin discovers how these mechanisms work and reveals them to his readers he frequently expresses his awe with phrases like "beautiful contrivance" (p. 13), "liveliest admiration" (p. 23), "one of the most wonderful cases of adaptation which has ever been recorded" (p. 44), "so complex, so apparently artificial, and yet so admirable an arrangement" (p. 208), "wonderful and often beautiful productions" (p. 224), and "beautiful adaptations" (p. 282), and this is all without paying much attention to the beauty of the orchids themselves: The diagrams Darwin provides are generally stripped of the three sepals and the outer two petals to show only the parts of the orchid involved in cross-fertilization.

Descriptions of the ways in which animals and plants were precisely adapted to their environments was a common feature of British natural history long before Darwin came around. Under the influence of the Anglican version of natural theology, such adaptation was attributed to the acts of a divine Creator. This assumption can be found in the works of John Ray (1627 – 1705) through at least the 1830s, when even a very smart and famous 19th-century scientist could observe how the Creator deliberately set the length of the day and year to precisely fit the rhythms of terrestial plants and animals. (William Whewell, Astronomy and General Physics Considered with Reference to Natural Theology, 1833, pgs. 21-41)

Darwin's revolutionary move in The Origin of Species was to describe an alternative way of interpreting adaptation: Rather than a Creator making each individual species fit its environment, variations of species have resulted in accumulated changes based on survival and procreation. But for the most part, The Various Contrivances... is agnostic on how the reproductive mechanisms in orchids came about: At the outset of the book, Darwin assures his readers that "the study of organic beings may be as interesting to an observer who is fully convinced that the structure of each is due to secondary laws [e.g., natural selection], as to one who views every trifling detail of structure as the result of the direct interposition of the Creator." (p. 2)

Until the last chapter, only occasionly does Darwin interject his own interpretations based on natural selection. Sometimes he just can't help himself, as when discussing some parts of the orchid that perform no function:

In the last chapter, Darwin gives up trying to make the book acceptable to all worlds, and describes how the various types of orchids were the result of natural selection, but still with that sense of awe he had in describing the orchids themselves:

In the annals of evolution, one famous story comes from the writing and publication of The Various Contrivances.... In the first edition, Darwin discusses the Angræcum sesquipedale, "of which the large six-rayed flowers, like stars formed of snow-white wax, have excited the admiration of travellers in Madagascar" (1st ed, p. 197; 2nd ed, p. 162). He discovers a nectary in this species 11½ inches long, with nectar in only the lowest inch and a half. Darwin surmises that "in Madagascar there must be moths with probosces capable of extension to a length of between ten and eleven inches." (1st ed, p. 198)

Really? A moth with nearly a foot-long proboscis? You're kidding, right? So thought many readers of that first edition. But in the second edition, Darwin has been redeemed:

After reading The Various Contrivances..., I was more than ready to see The Orchid Show at the New York Botanical Garden in the Bronx, and Deirdre and I drove up there this morning. The exhibit designed by Raymond Jungles is simply amazing — an indoor creation of seveal environments, including rainforests and deserts, with many other plants accompanying a whole lot of different fascinating species of orchids of all sizes and colors and jaw-dropping beauty. Outside, the great weather this morning allowed observing beauty of another sort, because scattered about the Botanical Garden were 19 bronzes by everyone's favorite modern sculptor, Henry Moore, dating from 1949 through 1984.

We then drove out to a place I had never been, City Island, which looks more like a Maine seaport town than a part of New York City, and where we had fried soft-shell crabs and fried shrimp from Johnny's Famous Reef Restaurant, sitting outside on the south-end tip of the island, and got home just as the light rain was beginning, so as not to spoil quite a lovely day.


Comments:

Hello!

Very Interesting post! Thank you for such interesting resource!

PS: Sorry for my bad english, I'v just started to learn this language ;)

See you!

Your,

— Raiul Baztepo, Sat, 28 Mar 2009 21:03:36 -0400 (EDT)


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