Different morphological features of the Frenelopsis from a Torrelaguna bassin (Madrid, Spain) are described and compared with F. alata and F. oligostomata , studied by other authors. The Frenelopsis rests present, in the studied deposit, a remarkable polymorphism with respect 10 the dimensions of the leaves, but all the specimens studied are greatiy related to F. oligostomata . The chemical study of the organic constituents of the cutic1es shows a heterogeneous composition, being the major constituents an alkali-insoluble cutinized residue and a likehumic acid polyphenolic extractable fraction, Cuticles contains a certain proportion of a highly alterated lignin-like polymer, and minimal amounts of fulvic acids, nitrogenated compounds, free hydrocarbons and carbohydrates. KEY WORDS: Hystology, Biochemistry, Frenelopsis, Upper cretaceous, Palaeobotany, Humic substances.