The cuticles of some Angiosperm leaves and fruits

The cuticles of twenty-four species from a wide range of mono- and di-cotyledonous plants were examined by chemical methods. The cuticles differ markedly in the amount and composition of the surface wax, in the thickness of the cuticular membrane, and in the content and composition of the cutin of the membrane. Fruits usually have heavier wax deposits and much thicker membranes than leaves. No direct relationship exists between surface waxiness and thickness of the membrane. Alkanes and primary alcohols are prominent in many of the surface waxes; triterpenoids occur less frequently. The cutin content of the membrane varies considerably; a delicate membrane tends to have a low content of cutin in which fatty acids are prevalent, and a well-developed membrane a higher content of cutin more rich in hydroxy-fatty acids. 10,16-Dihydroxyhexadecanoic acid is often an important constituent of cutin; 9,10,18-trihydroxyoctadecanoic acid is most prominent in the cutin of thicker membranes. The possible influence of the variations in cutin acids upon the structure of cutin and the taxonomic implications of wax and cutin composition are discussed.