Definition: Siphonogamous plants (Siphonogams) are defined by the presence of a pollen tube (siphon) that delivers male gametes to the female gamete (egg).

Inclusive Term: This category includes both Angiosperms (flowering plants) and Gymnosperms (non-flowering seed plants).

Seed Production: Since both Angiosperms and Gymnosperms are Spermatophytes (seed-bearing plants), all siphonogamous plants produce seeds.

Evolutionary Context: This reproductive mechanism allowed plants to fertilize without the need for external water, which is necessary for "lower" plants like Pteridophytes.