1911 Encyclopædia Britannica/Blackberry
BLACKBERRY, or Bramble, known botanically as Rubus fruticosus (natural order Rosaceae), a native of the north temperate region of the Old World, and abundant in the British Isles as a copse and hedge-plant. It is characterized by its prickly stem, leaves with usually three or five ovate, coarsely toothed stalked leaflets, many of which persist through the winter, white or pink flowers in terminal clusters, and black or red-purple fruits, each consisting of numerous succulent drupels crowded on a dry conical receptacle. It is a most variable plant, exhibiting many more or less distinct forms which are regarded by different authorities as sub-species or species. In America several forms of the native blackberry, Rubus nigrobaccus (formerly known as R. villosus), are widely cultivated; it is described as one of the most important and profitable of bush-fruits.
For details see F. W. Card in L. H. Bailey’s Cyclopedia of American Horticulture (1900).