TERPENOIDS 267 



The tribe Helenieae, on morphological grounds (Chapter 3) 

 appears to be artificially circumscribed, and it should prove interest- 

 ing to extend comparative biochemical studies of the sesquiterpenes 

 to other groups of this tribe, particularly to those which are believed 

 to have their relationship with other elements of the Compositae^ (for 

 example, a comparison of Sartwellia, currently placed in the Helenieae, 

 with Haploesthes of the Senecionieae, and so on. Turner and John- 

 ston, 1961). 



^ Chemists may not fully understand the taxonomist's hesitancy in making such 

 redispositions from the provocative chemical data at hand. However, evidence bearing on 

 phylogeny is often apparently conflicting, usually circumstantial, rarely unequivocal, and 

 basic conservatism is required. Yet taxonomic and chemical correlations reflected in the 

 sesquiterpenes of the Compositae may eventually be utilized to decide between two con- 

 flicting points of view even when the chemical data support the more radical departure 

 from the existing treatment of the group. 



