Floral colours and their origins

Abstract

A new orientation is given to the subject of floral colours by the author’s discovery that these colours may be placed into two distinct spectral categories, which have been designated by him respectively as the spectrum of florachrome A and of florachrome B. Typical of these two categories are the colours ofDelphinium ajacis (larkspur) in the blue and pink varieties respectively, the former showing the spectrum of flora-chrome A and the latter that of florachrome B. As a general rule, all blue flowers exhibit the spectrum of florachrome A which consists of three distinct and clearly separated bands of absorption appearing respectively in the red at 630 mµ, in the yellow at 580 mµ and in the green at 540 mµ. The spectrum of florachrome B also consists of three distinct bands of absorption, but these now appear in the orange-yellow at 590 mµ, in the green at 545 mµ and in the blue-green at 505 mµ. Spectra exhibiting these features are reproduced with the paper. Their explanation is discussed and it is shown that they owe their origin to an electronic absorption frequency located at the first of the three bands combining with vibrational transitions, the oscillator being the CO group present in the structure of the florachrome.