This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Trees or shrubs, the bark exuding gum, the foliage, bark and seeds containing prussic acid, bitter. Leaves alternate, petioled, serrate, the small stipules early deciduous, the teeth and petiole often glandular. Flowers corymbose, umbelled, racemed or solitary, regular, mostly perfect. Calyx inferior, deciduous, free from the ovary, its tube obconic, campanulate or tubular, 5-lobed. Disk annular. Calyx-lobes imbricated in the bud. Petals 5, inserted on the calyx. Stamens numerous, inserted with the petals. Pistil 1 in cur genera; ovary 1-celled, 2-ovuled; style simple; stigma mostly small and capitate. Fruit a drupe. Seed I, suspended; endosperm none; cotyledons fleshy.
About 10 genera and 120 species, widely distributed, most abundant in the north temperate zone.
Flowers umbellate or corymbose, appearing before or with the leaves mostly on branches of the
Flowers racemose, appearing after the leaves on branches of the year.