Such inflorescence in which the main axis is elongated and bears sessile flowers is called:

Explanation

The inflorescence in which the main axis is elongated and bears sessile flowers is called a spike. In a spike, the flowers are arranged in an acropetal manner, which means that the lowermost flowers mature first and the upper ones mature later. The flowers are directly attached to the main axis without any pedicels or stalks. Examples of plants with spike inflorescence include wheat, rye, and barley.