Eucalyptin and 8-desmethyleucalyptin have been isolated from the leaf wax coatings of several species of Eucalyptus, from Syncarpia glomulfera, Lophostemon confertus and an Angophora hybrid indicating that C-methylated flavones may be fairly distinctive of the family Myrtaceae. Ursolic acid has been isolated from the leaf waxes of E. youmanii, S. glomulifera, Leptospermum petersonii and Melaleuca quinquenervia, friedelin from Lophostemon confertus and 4,6-dimethoxy-2-hydroxyacetophenone from E. michaeliann. Earlier reports on the occurrence of two unusual Cmethylflavones, eucalyptin (4',7-dimethoxy-6,8-dimethyl-5hydroxyflavone) and 8-desmethyleucalyptin in the leaf waxes of several species of Eucalyptus and of the botanically very closely related Angophora [ 1,2] prompted us to extend the investigation to additional species of Eucalyptus spread widely throughout the genus (according to Pryor and Johnson's classification [3] ) as well as to other myrtaceous genera.Eucalyptin was obtained, albeit in vastly varying amounts (Table l), from E. eximia Schau. (but not from the flower bud wax coating), E. gummferera (Gaertn.) Hochr. and E. maculata Hook. (subgenus Corymbia), E. elata Dehnh., E. haemastoma Sm., E. luehmanniana F. Muell. and E. youmanii Blakely and McKie (subgenus Monocalyptus), E. michaeliann Blakely (subgenus Symphyomyrtus) as well as from a hybrid Angophora hispida (Sm.) Blaxell x A. bakeri C. Hall ( = 'A. clelandii' Maiden). The less common 8-desmethyleucalyptin accompanied eucalyptin in the leaf waxes of E. michaehana and E. youmanii. Neither flavone was present in sufficient quantity for isolation in either E. peltata Benth. (subgenus Corymbia) or E. staigeriana F. Muell. ex F. M. Bail. (subgenus Symphyomyrtus) although TLC showed in both cases very faint spots of R, values identical with those of eucalyptin.Among other myrtaceous species eucalyptin has been isolated from Syncarpia glomulifera (Sm.) Niedenzu and 8-desmethyleucalyptin from Lophostemon confertus (R. Br.) Peter Wilson and J. T. Waterhouse (syn. Tristania conferta R. Br. [4]). Neither flavone appeared to be present in the leaf waxes of Melaleuca quinquenervia (Cav.) S. T. Blake, M. leucadendron (L.) L. or Leptospermum petersonii F. M. Bail.The ubiquitous ursolic acid has been isolated from the leaf waxes of E. youmanii, S. glomulifera, M. quinquenervia and Leptospermum petersonii, whilst friedelin and 4,6 dimethoxy-2-hydroxyacetophenone were obtained from Lophostemon confertus and E. michaeliana waxes, respectively.In addition to our results eucalyptin has also been reported from the foliage of E. citriodora F. Muell. [5] as well as from the two myrtaceous species Myrcia citrifolia (Aubl.) Urb. and Eugenia btyora (L.) DC. [6], although in neither case was any mention made of whether it was present in the leaf wax coating. More recently eucalyptin, 8-desmethylepcalyptin, sideroxylin (4',5-dihydroxy-6,8 dimethyl-7-methoxyflavone) and 8-desmethylsideroxylin have been reported from the leaf coating of several additional species of Eucalyptus [7]. Sideroxylin has been originally obtained from the leaf parenchyma of E. sideroxylon A. Cunn. ex Woolls [S] and E. dundasii Maiden [ 93.It thus appears that C-methylflavones are distributed throughout both subfamilies of the Myrtaceae: the Myrtoideae (Eugenia, Myrcia) and Leptospermoideae (Angophora, Eucalyptus, Lophostemon, Syncarpia) and that they are probably quite distinctive of the whole family. However, their chemotaxonomic significance is somewhat diminished owing to the occurrence of all four earlier mentioned flavones in the epicuticular leaf coating of Kalmia latifolia L. (Ericaceae) [7] and of strobochrysin (5,7-dihydroxy-6-methylflavone) in the heartwood of Pinus strobus (Pinaceae) [lo]. Of the 15 related Cmethylflavonols [ 11) two occur in the family Polypodiaceae (Pteridophyta), three in the Pinaceae (Gymnospermae) and 10 in the Didieraceae, an angiosperm family botanically far removed from both Myrtaceae and Ericaceae.It is interesting to note that 4,6-dimethoxy-3,5 dimethyl-2-hydroxyacetophenone, a putative precursor of some of these flavones, has been reported from the volatile leaf oil of Melaleuca cajuputi Powell [ 121. Also a compound (mp 184185") named 'eucalyptin', isolated independently by Elkeiy et al. [13] from the foliage of Eucalyptus citriodora and E. globulus at about the same time as the investigation of Lamberton et al. [ 1,2], is not, according to the authors, a flavonoid but may be a coumarin.