TERPENOIDS 259 



tail (Korte, 1955b). A comprehensive treatment of the results is 

 presented in Table 13.4. This family is characterized by the presence of 

 cardenolidglycosides, alkaloids, and neutral bitter principles. 



The sub-family Plumieroideae is separated into several sub- 

 tribes which, in addition to their morphological characters, may be 

 distinguished on the basis of their chemistry. For example, Plumiera 

 is characterized by the bitter principle, plumierid; Holarrhena 

 through steroidal alkaloids such as conessin; and other genera 

 through particular alkaloids. In the sub-tribe Tabernaemontaninae 

 the alkaloid tabernimontanin is always present, but cardenolidglyco- 

 sides are absent. In the second sub-family, Echitoideae, cardenolid- 

 glycosides are common, but only the sub-tribe Parsoniae produces 

 steroid alkaloids such as conessin, and this sub-tribe appears to be, in 

 its chemistry, more closely related to the sub-tribe Alstoniinae of the 

 Arduineae. Conversely, the sub-tribe Melodininae appears to be 

 related to the tribe Echitideae since the former is the only one of its 

 sub-family producing cardenolidglycosides. 



An interesting situation is presented by the family Oleaceae, 

 included in the order Contortae by Engler and Diels (though distin- 

 guished as a separate sub-order, Oleineae). Wettstein excluded the 

 Oleaceae from the Contortae and derived them from the order Tubi- 

 florae. Hutchinson included the family in the order Loganiales while 

 Hallier derived the Oleaceae from the Scrophulariaceae and the 

 Contortae from the Linaceae. It is obvious that these proposals 

 incorporated widely divergent views on the position of the Oleaceae 

 on the basis of morphological data. 



Korte (1954) found that the Oleaceae differed greatly, in their 

 chemistry, from other famihes of the Contortae. The Oleaceae, which 

 are usually not bitter, contain no alkaloids but rather contain the 

 characteristic phenohcs fraxin and syringin, entirely different types of 

 substances. The other members of the Contortae do not produce fraxin 

 or syringin and instead are prolific in the formation of bitter principles, 

 cardiac poisons, and alkaloids. According to Korte: 



From the standpoint of their bitter substances and in agreement with 

 the system of Wettstein the order Contortae now without doubt is 

 subdivided into the following families: Gentianaceae, Menyanthaceae, 

 Loganiaceae, Apocynaceae and Asclepiadaceae. 



Recently, work on certain sesquiterpenes of the Compositae 

 by Herz and coworkers has disclosed a number of taxonomically in- 

 teresting correlations, and an intensive study of these compounds 

 may provide new insights into the relationships among certain tribes 

 of this family. 



