Historical Perspectives on Heterostyly

Abstract

Heterostyly was recognized as a morphological feature of certain groups of flowering plants as early as the 16th century, when it was reputedly noted in Primula by Clusius (van Dijk 1943). Few, if any, attempts were made to interpret the adaptive significance of this floral heteromorphism until Charles Darwin and Friedrich Hildebrand studied the phenomenon just after the middle of the 19th century. In 1862 Darwin published his first paper on dimorphic primulas and their “remarkable sexual relations”, and in 1863 Hildebrand published his initial observations on Primula sinensis. In his 1862 paper, Darwin introduced, but then abandoned, the horticultural terms “pin-eyed” and “thrum-eyed” (erroneously as “thumb-eyed”) to refer to the long- and short-styled floral morphs of Primulas. Many subsequent authors, for the sake of brevity, have adopted the terms pin and thrum, although these are applicable only to the flowers of dimorphic species and not of trimorphic ones. Thus, if both distylous and tristylous species are under discussion, referring to the morphs as long-, mid-, and short-styled or Longs, Mids, and Shorts is the most economical terminology.