Alder Plural . Name of many trees of the family Betulaceae . In fact, there are several species that are known by that name, those belonging to the genus Alnus. There are approximately 30 species and are distributed all over the world. Trees of the genus Alnus of the family Betulaceae . In South America are the species Alnus acuminata and Alnus jorullensis and in Europe, basically the Alnus glutinosa.
