PHENOLIC SUBSTANCES 21 1 



OH 



Thus, in Myrtales, the tri-hydroxy configuration is expressed within 

 several phenohc classes and is emphasized to the extent that it 

 assumes some systematic significance. Bate-Smith noted that 

 among the six sub-families of the Rosaceae proposed by various 

 authors, four (Spiraeoideae, Pomoideae, Prunoideae and Rosoideae) 

 contain only leucocyanidin while one (Chrysobalanoideae) contains 

 both leucocyanidin and leucodelphinidin. Bate-Smith noted that the 

 last-named sub-family had been treated as a family by at least 

 one worker. 



The situation described above emphasizes one of the most 

 vexing problems facing the systematist, regardless of whether or not 

 he is concerned with biochemical data, namely, the proper systematic 

 evaluation of a particular correlation which has been established. In 

 this case the Chrysobalanoideae as well as the other sub-families of 

 Rosaceae have already been recognized as distinctive on morpho- 

 logical grounds, and in fact most have been treated as separate 

 families on occasion (Lawrence, 1951). The question is how much 

 additional distinctiveness is implied by the presence of leucodelphini- 

 din in this sub-family alone (information was not available for the 

 Neuradoideae). Unfortunately, we are not yet in a position to give un- 

 qualified opinions in many cases such as this, but conservatism with 

 respect to the systematic evaluation of leucoanthocyanins is justifiable. 



In his general article on the taxonomic aspects of phenolics 

 Bate-Smith (1958) noted that three classes of these compounds are 

 widespread in their distribution in leaves of higher plants. These sub- 

 stances are leucoanthocyanins, flavonols and hydroxycinnamic acids. 

 He concluded that perhaps the absence of certain of these common 

 substances might be more significant than their presence. For in- 

 stance, leucoanthocyanins are for the most part absent from the orders 

 Centrospermae, Umbelliferae, and Contortae; entirely absent from 

 the Rhoeadales, Tubiflorae, Plantaginales and Cucurbitales; and al- 

 most entirely absent from the Campanulatae. They are also absent 

 from many families of the Ranales. Many of these same orders do not 

 produce flavonols. In connection with his discussion of flavonols Bate- 



