MISCELLANEOUS COMPOUNDS 279 



A number of different betacyanins occur but the differences 

 are thought to involve the nature of the glycoside rather than the 

 basic ring structure. Betanin and amarantin are most often encoun- 

 tered, while certain others are at present indicated to be genus 

 specific. In some cases the compounds are quite variable within a 

 genus or even within a species. For example Reznik (1957) found 

 sixteen different betacyanin type components in beets and turnips. As 

 an illustration of the intra-specific variation, the turnip cultivar 

 "Frankes Rekord" contained eleven different betacyanins and betax- 

 anthins while the cultivar "Kirches Ideal" contained only two of the 

 pigments. 



It is especially interesting that there is no known case of the 

 coexistence in the same plant of anthocyanins and betacyanins. 

 Typical anthocyanins are common in the Caryophyllaceae. Flavonols, 

 which are chemically quite close to the anthocyanins, are common in 

 the betacyanin-containing species (Reznik, 1957). This distribution 

 may indicate a functional equivalence between the brightly colored 

 betacyanins and anthocyanins despite their chemical differences, sug- 

 gestive that color rather than some cryptic metabolic role may account 

 for the presence of anthocyanins. 



One of the most unusual confirmations of the systematic im- 

 portance of a group of compounds is represented by the correlations 

 noted independently by Taylor (1940). Using rain water, gasoline 

 from a motor boat, and other crude techniques Taylor surveyed the 

 pigments of thirty-six species of flowering plants of Indefatigable 

 Island in the Galapagos, and twelve species were found to contain 

 "nitrogenous anthocyanins." Those species testing positive were in the 

 Centrospermae. 



Ordinarily, major taxonomic importance would not be ac- 

 corded a single chemical character, but the totally different structures 

 of the two types of pigments, betacyanins and anthocyanins, which indi- 

 cate different synthetic pathways, their mutual exclusion, and the lim- 

 ited distribution of the betacyanins make the presence of betacyanins 

 of particular taxonomic significance. In this connection, it is interesting 

 to note that Mabry et al. (1963) suggested that the order Centro- 

 spermae (Chenopodiales), as classically constituted and including the 

 Cactales, be reserved for the betacyanin-containing families, and that 

 those anthocyanin-containing families such as the Caryophyllaceae 

 and lUecebraceae be treated as a separate phyletic group whose 

 relationship is close but not within the betacyanin producing order. 



Tannins: Although tannins have been studied intensively 

 for many years, there has been no important biochemical systematic 

 study involving this group of compounds. Tannins are found in a wide 

 variety of plants, including algae, fungi, mosses, and ferns. Tannins 



