DOCTRINE OF ORCiANIC p]VOLUTION 437 



Fig. 300. — Family tree of Ranunfiilarpa', illustrating the evolution of the 

 group as provi.sioiially suggested in the text (pp. 4.37-440). 



into one plane, is shown in Fig. 300. If our idea of the kin.ship of 

 the different genera be correct, this diagram represents the branch- 

 ing lines along which we may suppose these members of the family 

 to have evolved. All that lies below the terminal twigs is supposed 

 to be buried; and, in a general way, the further a branch or line of 

 descent extends to the right the more is it supposed to depart from 

 the original ancestral form. 



Our vertical diagram thus indicates that of all the living forms 

 of RanuneulaceEe, Caltha most nearly resembles the ancestor of the 

 family. According to this view the story of the family's evolution 

 would be somewhat as follows. Among the descendants of Caltha- 

 like moisture-loving plants which grew in a remote geologic age, 

 some retained for innumerable generations the characteristics 

 which fitted them for living under the comparatively uniform con- 

 ditions afforded bj' protected moist situations, and are represented 

 to-day by our marsh-marigolds. In these have survived a most 

 primitive type of flower, hypogynous, with many-o\'uled, distinct 



