1. In orchid flowers, a sticky disc at the end of the stalk of the pollinium, by which it is attached to an insect's head.
2. A sticky substance in flowers used to collect pollen or pollinia; entomological orchid pollination uses the viscidium dually.

When an insect initially becomes engaged with a second flower of a compatible species, the viscidium of this flower grabs the pollinia off of the host insect's back or head and sends the genetics down the column to the ovary of the flower which is located in the stalk.

If the insect is lacking pollinia clusters to implant into the viscidium, it simply receives a coating of sticky matter which will in return collect pollinia from the anther cap as it disengages the flower.