Carnauba wax, found on the leaves of the wax-palm (_Copernicia cerifera_) contains ceryl alcohol (C_{23}H_{53}OH) and myricyl alcohol (C_{30}H_{61}OH) esters of cerotic acid (C_{25}H_{51}·COOH) and carnaubic acid (C_{23}H_{47}·COOH). It is the best known vegetable wax. Poppy wax is composed chiefly of the ceryl ester of palmitic acid (C_{17}H_{35}·COOH). Since waxes contain no glycerol, they give no odor of acrolein when heated with dehydrating agents, do not become rancid, and are less easily hydrolyzed than the fats. They are soluble in the same solvents as the fats, but generally to a less degree. The facts that waxes are impervious to water and usually occur on the surfaces of plant tissues have led to the conclusion that their chief function is to provide against the too-rapid loss of water by evaporation from these tissues. This seems to be borne out by the common experience that many fresh fruits and vegetables will keep longer without shriveling if their waxy coating is undisturbed. No other function than that of regulation of water losses has been suggested for the plant waxes. C. THE LIPOIDS The lipoids, or "lipins," as some authors prefer to call them, are substances of a fat-like nature which are found in small quantities in nearly all plant and animal tissues and in considerable proportions in nerve and brain substance, in egg yolk, etc., and in the seeds of plants. When hydrolyzed, they yield fatty acids or derivatives of fatty acids and some other group containing either nitrogen only or both nitrogen and phosphorus. The facts that they are extracted from tissues by the same solvents which extract fats and that they yield fatty acids when hydrolyzed account for the name "lipoid," which comes from the Greek word meaning fat. Some writers, who object to the word "lipoid" as a group name, prefer to call these substances the "fat-like bodies." The first group of lipoids to be studied were those which occur in the brain; and the name _cerebroside_ was given to those lipoids which, when hydrolyzed, yield fatty acids, a carbohydrate and a nitrogen-containing compound but no phosphoric acid; while those lipoids which contain both nitrogen and phosphorus were called _phosphatides_. Substances which correspond in composition to both these types are found in plant tissues and the same class names are applied in a general way to lipoids of either plant or animal origin. Plant lipoids have not been studied to nearly the same extent as have those which occur in the animal body; and certain observers believe that there are significant differences between the lipoids of plants and those of animal origin. However, most investigators use the same methods of study and the same systems of nomenclature for these fat-like substances, regardless of their origin. LECITHIN