What is the primary feature of pistillate flowers in spike inflorescence?

The primary feature of pistillate flowers in spike inflorescence is that they are found in the axils of upper leaves. In this type of inflorescence, the flowers are arranged along a continuous spike without significant spacing, and the pistillate (female) flowers, which are responsible for seed production, typically develop in these locations on the stem.

This arrangement allows for efficient pollination and seed formation, as the close proximity of flowers facilitates the transfer of pollen. The presence of the flowers in the axils of upper leaves can also maximize exposure to pollinators and sunlight, which are crucial for successful reproduction. The positioning directly influences the plant's reproductive success and adaptation to its environment.