Darwin's Sexy Orchids: A Life Full of Orchids

 
 

Darwin’s most famous orchid arrived in a “mystery box” from James Bateman on January 25, 1862, while he was reading proofs for the book.

Darwin wrote to Hooker: “I have just received such a Box full from Mr Bateman with the Astounding Angraecum sesquipedalian with a nectary a foot long—Good Heavens what insect can suck it”?

Experiments had to be done:

  • Bristles and needles (no success)
  • Cylinder to which the pollinia attached themselves
  • Conjectured that there was a moth with a long proboscis that could get the nectar from the bottom of the nectary

Darwin wrote:

“The astonishing length of the nectary may have been acquired by successive modifications. As certain moths of Madagascar became larger through natural selection . . . those individual plants of the Angræcum which had the longest nectaries . . . and which, consequently, compelled the moths to insert their proboscises up to the very base, would be fertilised. . . . These plants would yield most seed, and the seedlings would generally inherit longer nectaries; and so it would be in successive generations of the plant and moth. Thus it would appear that there has been a race in gaining length between the nectary of the Angræcum and the proboscis of certain moths.”


 

 

It took until 1903 for Xanthopan [Macrosila] morgani Walker (1856) supsp. praedicta Rothschild & Jordan (1903) to be discovered and described, and not until the 1990s for it actually to be observed pollinating an A. sesquipedale.

Darwin continued his research on orchids for the remainder of his life, publishing revisions in 1877 and 1882, along with several articles. He also heated his first greenhouse and added more, and on the receipt of one particularly nice shipment from Kew reported, “Henrietta & I go & gloat over them."

Darwin showed:

that Orchids exhibit an almost endless diversity of beautiful adaptations. When this or that part has been spoken of as contrived for some special purpose, it must not be supposed that it was originally always formed for this sole purpose. The regular course of events seems to be, that a part which originally served for one purpose, by slow changes becomes adapted for widely different purposes.

In my examination of Orchids, hardly any fact has so much struck me as the endless diversity of structure,—the prodigality of resources,—for gaining the very same end, namely, the fertilisation of one flower by the pollen of another. . . [I] found the study of orchids eminently useful in showing me how nearly all parts of the flower are coadapted for fertilisation by insects, & therefore the result of n. selection,—even most trifling details of structure.

 

Warner, Robert and Benjamin Samuel Wiliams. The orchid album: comprising coloured figures and descriptions of new, rare, and beautiful orchidaceous plants.  London:  B.S. Williams, 1882-96.

Select bibliography:

  • Allan, Mae. Darwin and his flowers: the key to natural selection (New York: Taplinger, 1977)

  • The complete works of Charles Darwin online (http://darwin-online.org.uk/)

  • Darwin Correspondence Project (http://www.darwinproject.ac.uk/)

  • Darwin’s garden: an evolutionary adventure (New York: New York Botanical Garden, 2008).

  • Porter, Duncan M. (various journal articles)

  • The works of Charles Darwin (New York: New York University Press, 1988). 29 vols.