From Goethe's plant archetype via Haeckel's biogenetic law to plant evo-devo 2016.

In 1790, the German poet Johann W. v. Goethe (1749-1832) proposed the concept of a hypothetical sessile organism known as the 'Plant Archetype,' which was subsequently reconstructed and depicted by 19th-century botanists, such as Franz Unger (1800-1870) and Julius Sachs (1832-1897), and can be considered one of the first expressions of Evo-Devo thinking. Here, we present the history of this concept in the context of Ernst Haeckel's (1834-1919) biogenetic law espoused in his Generelle Morphologie der Organismen of 1866. We show that Haeckel's idea of biological recapitulation may help to explain why various phenomena, such as the ontogenetic transformations in the stellar anatomy of lycopods and ferns, the transition from primary to secondary anatomy of seed plants, the presence of unfused juvenile cone scale segments in the Japanese cedar (Cryptomeria japonica), and the transition of C3- to C4-photosynthesis in the ontogeny of maize (Zea mays), appear to support his theories. In addition, we outline the current status of plant evolutionary developmental biology (Evo-Devo), which can be traced back to Haeckel's (1866) biogenetic law, with a focus on the model plant thale cress (Arabidopsis thaliana).