Unlike most other plants the pollen grains of orchids stick together and form masses called pollinia . The illustration on the right shows the pollinia of Disa atricapilla. The sticky viscidium, which helps the pollinia stick to pollinators is also visible. The ovary, when cut open, contains numerous tiny ovules, which in the mature capsule develop into dust-like seeds. These are normally dispersed by wind, but water dispersal has recently been observed in Disa uniflora and related species.
Orchids have a symbiotic relationship with fungi that live in their roots, called mycorrhiza .
The fungi supply the orchid with nutrients which they absorb from the dead organic matter. Mycorrhiza symbioses are also known in other plants like for example forest trees, although these are less dependent on their fungi. There are even some orchids which are yellow-brown as they do not have chlorophyll and obtain all their essential nutrients from the fungi. They are termed saprophytes.