Also known as Rubus fruticosus caesius. The fruit is reminiscent of a raspberry, but is usually purple or black instead of red. They are commonly found in the Northern hemisphere, and the leaves can be used for tea.
Nicholson, George The Illustrated Dictionary of Gardening, Div. VI (London, England: L. Upcott Gill, 1884)
Courtesy the private collection of Roy Winkelman