Darwin's Sexy Orchids: Specimens From Around The World

Catasetum macrocarpum (as C. claveringii)

Catasetum macrocarpum (as C. claveringii) in [Edwards’s] Botanical Register, vol. 10 pl. 840 (London:James Ridgway, 1824). Set purchased in London in 1928 by Garden founder Susanna Bixby Bryant.

After completion of his research about British orchids, Darwin went on to examine specimens from other parts of the world, many of which species had been sent to Europe during the great 19th century plant collecting “craze.”

A number of prominent British orchid growers (including Hooker at Kew) sent him specimens to examine, although of course the pollinators in most cases were unknown

He was particularly fascinated with the genus Catasetum, calling it “the most remarkable of all Orchids", and showed how in these flowers "as throughout nature, pre-existing structures and capacities [had been] utilised for new purposes".

Catasetum tridendatum showed its “truly marvelous” mechanism, by which it shot out a pollinium at any insect touching a part of the flower with “sticky gland always foremost.”

Darwin imitated the action of an insect touching the flower’s “antenna” using a whalebone spring.

    I touched the antennæ of C. callosum whilst holding the flower at about a yard's distance from the window, and the pollinium hit the pane of glass, and adhered to the smooth vertical surface by its adhesive disc.

Catasetum macrocarpun (as C. tridentatum)

C. macrocarpum (as C. tridentatum) in Curtis's Botanical Magazine, vol. 61 pl. 3329 (1834).
C. marcocarpum (as Monachanthus viridis)

C. macrocarpum (as Monachanthus viridis) in Edwards's Botanical Register, vol. 21 pl. 1752 (1836).

He conducted experiments to determine just what caused a pollinium to be released, including:

  • Fall onto a table from a height of 2-3 in.
  • Cut off with a crash with scissors
  • Deep pricks of the column and stigmatic chamber
  • A blow hard enough to knock off the anther (an accident)
  • Press hard on pedicel and rostellum
  • Nothing works except “violence” to the antennae (not including stream of air, cold water or human hair)

He also solved the “problem” of Catasetum macrocarpum [=tridentatum], flowers of which had been described not only as three separate taxa, but in three genera.  Lindley had stated, “Such cases shake to the foundation all our ideas of the stability of genera and species.

These Darwin determined were just male, female, and perfect flowers on the same plant sometimes at different times.

Catasetum macrocarpum Rich. ex Kunth (1822)

IPNI

  • Monachanthus viridis Lindl. (1832) =Catasetum trifidum Hook. (1833)
  • Monachanthus viridis Schomb. (1831) =Catasetum barbatum Lindl. (1844)
  • Monachanthus viridis Lindl. (1836 publ. 1835) =C. macrocarpum FEMALE
  • C. tridentatum Hook. (1823) =C. Macrocarpum MALE
  • C. tridentatum, var. viridiflorum (1834) FEMALE?
  • Myanthus barbatus Lindl. (1836 publ. 1835) =C. barbatum BISEXUAL?
Darwin's Linnean Article

Darwin, Charles.  “On the three remarkable sexual forms of Catasetum tridentatum, an orchid in the possession of the Linnean Society.” [Read 3 April] Proceedings of the Linnean Society of London. Botany 6: 151-157. 1862.  Darwin read this paper, an extract from the book, the month before the book was published.

 

Darwin's Sexy Orchids: A Life Full of Orchids