238 BIOCHEMICAL SYSTEMATICS 



wherein oil characters differed among morphologically similar plants. 

 A notable example is the species Eucalyptus phellandra discussed 

 prominently by Read (1944). According to Read, E. phellandra had 

 been included previously under E. amygdalina, and in the first 

 edition of the Baker and Smith work (1902) it was recorded under 

 amygdalina. According to Baker and Smith, "It is one of the few 

 species of this research that has been founded almost entirely on the 

 chemical constituents of the oil." There is then some circular reason- 

 ing if one creates a species on the basis of a difference in oil character 

 alone, while simultaneously maintaining that constancy of oil character 

 within a species is typical within species of the genus. As a generali- 

 zation the species constancy of oil character in Eucalyptus is doubt- 

 lessly accurate. Physiological races are regularly encountered, and 

 their appearance does not normally affect the integrity of the species. 

 In Pinus, Mirov (1961) has found that some species vary but little in 

 turpentine composition throughout their range while other species 

 are quite variable in this respect. 



In connection with problems of phylogeny within the genus 

 and among other related genera. Baker and Smith noted the similari- 

 ties in oil constituents of Eucalyptus and Angophora (for example, 

 the presence of the sesquiterpene, aromadendrene, in both genera) as 

 opposed to a third allied genus, Tristania. They proceeded to develop 

 a postulated line of descent showing the supposed origin of each sub- 

 group, the pattern stemming from correlated chemical and morpho- 

 logical characters. Baker and Smith recognized four major sub-divisions 

 of the genus with distinctive chemical attributes: 



(1) Those yielding oils consisting largely of the terpene pinene, 

 either dextro-rotatory or laevo-rotatory. 



(2) Those yielding oils containing varying amounts of pinene 

 and cineole, but in which phellandrene is absent. 



(3) Those yielding oils in which aromadendral is a character- 

 istic constituent and phellandrene is usually absent. 



(4) Those yielding oils in which phellandrene is a pronounced 

 constituent with piperitone mostly present. 



Since the majority of eucalypts yield oil largely of pinene 

 and cineole without phellandrene, the authors believed that phellan- 

 drene and thus piperitone appeared later, in fact even later than 

 aromadendral. 



An interesting correlative morphological character is found 

 among the Eucalypts. The character involves the pattern of leaf 

 venation which seems generally to be correlated with the oil constitu- 



