The loganberry is a hybrid produced by crossing a blackberry with what?

The loganberry is a hexaploid hybrid produced from pollination of a plant of the octaploid blackberry cultivar 'Aughinbaugh' (Rubus ursinus) by a diploid red raspberry (Rubus idaeus). The plant and the fruit resemble the blackberry more than the raspberry, but the fruit color is a dark red, rather than black as in blackberries. Loganberries are cultivated commercially and by gardeners.

Logan was unsatisfied with the existing varieties of blackberries and tried crossing two varieties of blackberries to produce a superior cultivar. He happened to plant them next to plants of an old variety of red raspberry, 'Red Antwerp', all of which flowered and fruited together. The two blackberry cultivars involved in these experiments were probably 'Aughinbaugh' and 'Texas Early' (a cultivar of Rubus velox), which were two of the three varieties that Logan had planted in his yard that year. Logan then gathered and planted the seed from his cross-bred plants. His 50 seedlings produced plants similar to the blackberry parent 'Aughinbaugh', but larger and more vigorous.