Catasetum

The colorful male and yellowish-green female flowers are typically situated on different plants, a phenomenon known as dioecy.

Initially, taxonomists thought they were dealing with different species, a puzzle which Charles Darwin resolved when writing Fertilisation of Orchids.

Sack-shaped Catasetum (Catasetum saccatum), a tropical South American species, discussed by Darwin, actually launches its viscid pollen sacs with explosive force, when an insect touches a seta.

Species of this genus all host wood-devouring mycorrhizal fungi which supplement the plants' nutrition by breaking down decomposing wood.

Most of these species have a prolonged saprophytic stage in decomposing wood as seedlings before developing leaves and photosynthesis.

Eulaema cingulata orchid bee showing pollinia attachment points of C. saccatum and C. discolor .
Illustration of C. saccatum 's (C) column cross section and (D-E) pollinia
Catasetum x faustoi (= C. longifolium x C. osculatum )