i26 Morphology BOOKI 



ing among botanists, for there was a somewhat widespread 

 opinion that the plants whose flower exhibits this feature are 

 a group which is truly monophyletic, and which represents 

 the highest development among Dicotyledons. The sym- 

 petaly of the corolla is but one peculiarity of a large division 

 of plants which show important marks of relationship in 

 other respects. 



In the subdivision of the Archichlamydeae Engler took 

 the view that the primitive form of the flower consisted 

 primarily of sporophylls which had mainly bracteal protec- 

 tion, or perhaps, rudimentary perianths. Advance there- 

 from he traced through such families as the Amentiferae 

 and other plants with naked flowers to those possessing 

 sepaloid perianths, and thence to the biseriate flowers, 

 among which he followed the gradual differentiation of 

 the most highly coloured petals, and most highly organized 

 flowers. Hence, the series started with the Piperales and 

 led up to the Umbelliflorae. 



It will be observed that in this arrangement Engler 

 departed from the view generally accepted by the followers 

 of the de Candollean tradition, that the flowers of the sim- 

 pler Ranunculaceae represent the primitive Angiospermous 

 type. The supporters of this view concluded that the 

 evolution of the flower had proceeded very far before the 

 Angiosperms appeared, and that the gradual development 

 of a perianth took place among the lower groups, appearing, 

 however, with a certain irregularity, and consequently not 

 being recognizable in every family. The flowers which 

 Engler claimed as primitive were held to have been derived 

 from forms with a perianth by a process of reduction, or 

 abortion of parts. 



To discuss the positions taken by these two schools of 

 thought would take us beyond the limits of this book. 

 Whether we accept Engler's view or not, it cannot be 

 denied that his arrangement presents a striking advance 



