Blackberries (Ribes fruticosus) are popular eaten fresh or made into jams, jellies or pastry fillers. When blackberries first develop, they are bright red and taste gritty and bitter. Once they mature, their pigment is dark purple to nearly black, and the flesh is juicy and sweet. Humans aren't the only fans of these fruits; birds, deer, raccoons and even bears feed on the berries. The structure of blackberries is similar to that of raspberries.
Overall Fruit Structure
While we may called the fruit a "berry," it truly is a clustered, cohesive cluster of many tiny fruits. Thus, a blackberry is often regarded as an aggregate fruit. Upwards of 60 to 100 tiny fruits comprise a ripe blackberry, according to Cornell University.
The tiny fruits or small dots within the blackberry are botanically known as drupelets. They have the same structure as drupe fruits like cherries or peaches, but on a much smaller scale. Close examination of an individual drupelet within the blackberry reveals a tiny seed with fleshy and juicy mesocarp and a thin skin or exocarp.
The drupelet arises from the pollination and fertilization of an ovary on the blackberry's flower. There are two chambers or ovules in each ovary, but one aborts and allows the other to ripen to form a blackberry fruit mass about four weeks after bees pollinate the blossom.