248 BIOCHEMICAL SYSTEMATICS 



"Thus, obviously, the Chamaecyparis-Cupressus group, to the chemist 

 appears to be less homogeneous than to the botanist." 



In generally evaluating the significance of the tropolones 

 Erdtman states, "Even at the risk of being criticized for wishful 

 thinking, one finds it hard to avoid the belief that tropolones have some 

 taxonomic significance." In another place he states, "The close 

 botanical similarity between the tropolone and non-tropolone Cupres- 

 saceae leads to the suspicion that the particular chemical differences 

 may indicate biosynthetic labihty rather than botanical diversity." 



Finally, Erdtman notes that, "It is possible to show chemical 

 overlappings between almost all genera of the family Cupressaceae." 

 He believes that this indicates that the family is an old one which has 

 retained ancestral compounds of a "Cupressaceae type" while the 

 individual genera and species have either lost or modified independ- 

 ently the pattern. 



The systematic botanist may inquire, with some justifica- 

 tion, how, in view of the preceding statements, the tropolones may 

 make a contribution to the systematics of the Cupressaceae. It is 

 true that the restriction of tropolones to the group is of systematic 

 interest but not, however, illuminating with respect to the placement 

 of the Cupressaceae. Below the family level, the tropolone content 

 varies qualitatively within a genus and the general heartwood chem- 

 istry of Chamaecyparis taiwanensis and C. obtusa, two species which 

 have been recorded as varieties, has been said to differ "completely" 

 by Erdtman. Also, in genera which have tropolone-containing species, 

 there are those which do not produce tropolones. It does not seem 

 likely that even rigorous characterization of heartwood constituents 

 has in this instance clarified significantly any of the relationships 

 within the Cupressaceae. If botanical and chemical opinions are cor- 

 rect, and the Cupressaceae constitute an old group whose present-day 

 genera are relicts, it is not surprising that a strictly comparative 

 chemistry fails to solve any major phylogenetic problems of the group. 

 The rare biflavonyls are found in Cupressaceae and may provide 

 further taxonomic insight (Chapter 11). 



Erdtman (1958) has presented a comprehensive treatment of 

 the heartwood chemistry of the Cupressaceae, summarized in Table 

 13-2. Some suggestions by Erdtman, based on the data, are that 

 Tetraclinis may be more closely related to the northern genera of the 

 Cupressaceae (that is, Heyderia) than to the southern genera; that in 

 the case of the two species of Heyderia it is tempting to separate them 

 at the generic level. Erdtman states: 



The similarities between Tetraclinis and Libocedrus decurrens and be- 

 tween Chamaecyparis nootkatinsis. Thuja, Biota and Libocedrus 

 formosana, the heterogeneity of Chamaecyparis and the great differ- 



