THE EVOLUTIONARY HISTORY OF PLANTS 305 



without making an unduly long chapter. Briefly, it may 

 be stated that the monocotyledons are the simplest and 

 probably the oldest angiosperms ; the dicotyledons are 

 higher in organization and came later. The descent and 

 various relationships of the families of dicotyledons can 

 be discovered by the study of the flower, fruit, and seed 

 better than by the examination of the vegetative organs. 



The entire pedigree of the several families cannot be 

 represented by arranging the names of the families in a 

 straight line. It is, however, in a general way, as indi- 

 cated by the succession of families in the Flora which 

 accompanies this book, the Willow Family being perhaps 

 the oldest (of the more familiar ones) and the Composite 

 Family the youngest. 



