They are perennial herbs with terminal inflorescences on leafy-shoots made up of congested bracts with each bract subtending a single or group of hermaphroditic flowers.

• 首先，表现在花粉在柱头上的萌发率和花粉管在花柱中的生长速率不同，远交花粉具有明显的优势，花粉萌发率高，萌发速度和花粉管生长速度都较快；