THE ORIGIN OF PETALS, 



and the Dicotyledons. These important classes are 

 distinguished from one another by several special 

 points of structure ; but the most striking one, so far 

 as regards our present subject, consists in the fact 

 that the Monocotyledons are generally arranged in 

 whorls of threes, while the Dicotyledons are generally 

 ananged in whorls of fives. At the present day, 

 the two modes of arrangement are often obscured in 

 various ways; for example, among some Monocotyle- 

 dons the stamens are doubled, or consist of two 

 separate whorls, while the petals and sepals are 

 coloured alike and are otherwise almost indistinguish- 

 able, so that the flowers seem at first sight to be 

 arranged by sixes rather than by threes ; and again, 

 among some Dicotyledons, one or more petals are 

 suppressed, or added, or all the petals are united into 

 a single circular or tubular corolla, so that the arrange- 

 ment seems at first sight to be by fours, or by eights, 

 or by threes rather than by fives. Originally, how- 

 ever, all Monocotyledons had a trinary arrangement, 

 while all Dicotyledons had a quinary arrangement ; 

 and these fundamental plans can still distinctly be 

 traced in by far the larger number of existing 

 species. 



So much by way of introduction. No\v^, since the 

 bright pigments of flowers usually reside in the petals, 

 and since petals have for their main if not for their 

 only function the display of such pigments as an 

 attraction for the fertilising insects, it is clear that we 

 must begin our inquiry by asking, — What was the 

 original colour of the organs from which petals were 

 developed } For we may take it for granted that the 

 primordial petals would at first follow the hue of the 



