QUINONES 229 



Rheum, as well as species of Atraphaxis, Oxygonum, Polygonum, and 

 Muhlenbeckia produce anthraquinones. More recently, Tsukida 

 (1957) reported on the distribution of anthraquinones in the Polygon- 

 aceae and added several other genera to those known to produce these 

 compounds. Jaretzky (1926, 1928) believed the presence of anthra- 

 quinones to be a primitive character since it was inversely correlated 

 with morphological progression within the genus Rumex (for example, 

 dioecious species such as Rumex acetosa are anthraquinone free) as 

 well as within the sub-family as a whole (for example, Fagopyrum 

 with heterostyly, is anthraquinone free). This is one of the few cases 

 where the presence of a particular class of chemical substances is 

 believed to be a primitive character. Tsukida was principally con- 

 cerned with the localization of specific anthraquinones in plant organs 

 as well as the specific anthraquinone types produced by these species, 

 and he did not emphasize particularly the systematic imphcations of 

 his data. 



Heppeler (1928) studied the distribution of emodin in the 

 genus Rhamnus (Rhamnaceae) and attempted a systematic arrange- 

 ment of the genus based on the presence or absence of this anthra- 

 quinone in dried plants. However, Maurin (1928) in the same year 

 reported a number of species positive which had been considered 

 negative by Heppeler. Furthermore, Hegnauer (1959) has noted that 

 the application of the Borntrager test to herbarium material is 

 unreliable since a number of species judged by Heppeler to be negative 

 have since been shown to contain anthraquinone. Hegnauer has 

 summarized present knowledge of the occurrence of anthraquinones 

 in the genus. Unfortunately (for purposes of phylogenetic implications), 

 a number of the series in both the sub-genera, Frangula and 

 Eurhamnus, which formerly had been considered negative, are now 

 shown to be positive for anthraquinones. It appears that anthra- 

 quinones are widespread in the genus Rhamnus and also in a number 

 of other genera of the Rhamnaceae. Since no distributional pattern is 

 now recognizable, further investigation on this family is recommended 

 by Hegnauer. 



In the Leguminosae only a few genera are known to produce 

 anthraquinones, but in one genus, Cassia, the compounds are wide- 

 spread. The classic anthraquinone work on Cassia is that of Gilg and 

 Heinemann (1926). These authors assumed that oxymethylanthra- 

 quinones were to be found only in the section Chamaesenna of the 

 sub-genus Senna. 



Within Chamaesenna the various series were analyzed for 

 presence of emodin-like anthraquinones, yielding some interesting 

 results. Probably the most noteworthy systematic conclusion stem- 

 ming from this survey was the redisposition of the taxa belonging 

 to the series Aphyllae, which includes only the two species, 



