20 



BIOCHEMICAL SYSTEMATICS 



Fig. 2-3. Diagram showing relationships between Araliaceae and 

 Unbelliferae. Horizontal lines mark beginning and end of Tertiary; 

 dotted lines connect morphological levels; solid lines indicate typo- 

 logical relationships; long double arrows signify actual relation- 

 ship; short double arrows indicate homologous (parallel) evolu- 

 tionary lines; oo, 5, 4, 3, 2, 1 = number of carpels; O = genus or 

 tribe; x = basic chromosome numbers; A = Araliaceae, Mc = 

 Myodocarpus, U = Umbelliferae, Ap = Apioideae, H = Hydro- 

 cotyloideae, S = Saniculoideae, M = Myrtales plexus, Ro = Rosales 

 plexus, Ra = Ranales plexus. Adapted from Baumann (Just, 1948); 

 copyright (1948) by the University of Chicago. 



is to D. chrysantha, but its actual phyletic relationship might be 

 closer to D. chrysantha, its extreme specialization being a result of 

 more rapid evolution from the phyletic line culminating in D. chry- 

 santha. D. scandens possibly diverged earlier from the chrysantha 

 stock, but diverged at a much slower rate (Fig. 2-5a and 2-5b). As in- 

 dicated by Stern (1961), "the angles of divergencies, etc. are strictly 

 diagrammatic and are not designed to denote constant rates of 

 divergencies of evolution." 



The Dicentra diagram was constructed primarily from inter- 

 pretations of exomorphic features. It is sometimes possible to con- 

 struct two-dimensional phyletic diagrams with assurance, often with 

 experimental support, when working with species groups where 

 hybridization, autoploidy, and amphiploidy have been major imme- 

 diate factors in the speciation process. The diagram for the genus 

 Clarkia by Lewis and Lewis (1955) is one of the better documented 



